Re: [Repeater-Builder] Desense with Notch-type duplexers - Questions
Cut the wire tied together TX and RX cables on the back of the quantar and seperate them as far as possible. On Fri, Aug 7, 2009 at 1:43 PM, tahrens301tahr...@swtexas.net wrote: Hi Folks, Guess it's a good thing the antenna party didn't happen yet. Put the DB-224 up on a pole here attached to a portable building. Ran the 7/8 heliax from the antenna into my garage - about 100'. With a signal source from my monitor, the repeater would chop in and out. Ugh-desense. I am using an old DBproducts 8 cavity notch-type duplexer. 4 on the receive, 4 on the transmit. The transmit side also has stubs. (see old thread). First, I used my spectrum analyzer sweep gen, and got what I thought were pretty good notches in the right places (depending if I was working on the xmit or rx side. According to the analyzer, the notch was about 70dB below the high point. However, I think that it was seeing the floor of the analyzer, not the real notch. Then, I hooked up a signal generator on one side, and a receiver on the other side, and tweaked a bit more for the least signal. All looked pretty good with definite notches, but it's obvious there's desense. All cables are double shielded. The system is 147.10/70, running about 60 watts out of the Quantar. Even running with battery-backup (20 watts), there's still some desense. Could it be that these cans are just not enough, or am I doing something wrong. Thanks! Tim Yahoo! Groups Links
RE: [Repeater-Builder] Desense on High Power Linear Repeater?
On Thu, 21 May 2009 08:06:38 -0400, Jeff DePolo j...@broadsci.com said: This leads me to a question that I have had on my mind. How are people doing desense testing with D-Star systems? (Remember, it's digital.) 73, Joe, K1ike How about this - record a clean D-Star transmission (not decoded, just the raw output from an FM receiver) on a PC with a good sound card, then use it to modulate the sig gen in your service monitor. Do desense test using a lossy tee like you normally would, except instead of comparing 12 dB SINAD points, you'd have to rely on listening to the repeated/decoded audio on another radio to gauge performance. Jeff's techniques should work. Another method is putting an IC-91AD or IC-92AD on extra-low power in a WELL SHIELDED box and passing it through a variable attenuator/iso-T with the best quality interconnect jumpers you can possibly muster, if you're cheap/frugal. We did this for baselining our system off the mountain, but haven't done it yet on the hill. The shielded box came from the cellular phone test lab industry, and didn't leak AT ALL. This isn't an ideal way to test, but it's better than nothing lacking real D-Star test equipment. IFR/Aeroflex just announced that they're releasing D-STAR capability into one of their new model Service Monitors in June also. List price is ... astronomical, of course. It also does TDMA 2-way systems and NXDN and all the other newer-ish commercial stuff. Is there any way to get pre-FEC and post-FEC BER metrics out of a D-Star repeater or user radio? Not that anyone's been able to find. There's a mystery pin on the serial connection at the repeater modules themselves that's labeled RSSI in the service documentation (usually found only in Japanese, but some english versions have wandered out), but most folks who've played with it think it's just a standard analog voltage from the receiver, and not any indication of how the digital side of the repeater is coping with thing. To add insult to injury, VOICE in the D-STAR data stream is HEAVILY forward error corrected, so to REALLY test it ... you need to feed the IC-91AD/IC-92AD some serial data from a PC and then COPY it on another receiver and PC to see when things really start to fall apart. You can KINDA hear when the voice becomes error-corrected, but feeding something like a 1000 Hz tone through it is useless... like in the cellular industry you need to feed real words through it and determine the copyability of that voice for yourself... or just use the completely garbled falling out point as your known test point. No one's found any documentation on what BER rate is needed to be reached (in the failing/downward direction) before the rigs go from copyable voice to garbled, but there's definitely a stage there where that happens in a CONTINUOUS transmission... the system can pick up if it re-syncs in that mode (mobile flutter/multi-path) but it often will NOT REPEAT if a signal STARTS OUT that way... digital hysteresis of some value... unknown. The UTAH VHF group has done the most accurate and useful engineering data on D-STAR I've seen yet... google for their website. Very civil debates have also raged on some lists about whether or not pre-amps help or hurt with the broad nature of the receiver's front-ends, and over time... as someone else pointed out, since these are mobiles in a box that's not shielded well, folks have figured out that the quality of the internal interconnect jumpers from the rear-panel N-connectors to the rigs themselves are pretty piss-poor in SOME bands radios. You pretty much just have to open yours up to find out, and of course, you're playing with fire for your warranty at that point, I suppose. Would have been nice if Icom had just spent a few extra bucks on a $2000 repeater and put some semi-rigid or at least good quality double-shielded stuff in there. Although most who've opened the 1.2 GHz modules have found good quality jumpers in those. The cheapness seems to be in the VHF/UHF modules. External amplifiers are also a bone of contention... the rigs and repeaters send a bit of a preamble prior to the start of real needed header data, and some have external amps on their D-STAR repeater modules with no particular problems... but ramp-up time/switching time is very criticial... the routing information (callsigns) is only really sent ONCE at the beginning of the transmission, and if it's lost, it's not like P25 where the Unit ID information is continuously interlaced in the data stream. Later, some folks found that the single transmitting callsign *is* interlaced but it's non-standard (not in the D-STAR specification) and something that obviously Icom decided to do, but doesn't contain the full four-callsign routing header... just the transmitting station's callsign. So yeah... there's some issues with it... but generally it's been fun to mess with it here... I've rattled on other lists about the Gateway and
RE: [Repeater-Builder] Desense on High Power Linear Repeater?
This leads me to a question that I have had on my mind. How are people doing desense testing with D-Star systems? (Remember, it's digital.) 73, Joe, K1ike How about this - record a clean D-Star transmission (not decoded, just the raw output from an FM receiver) on a PC with a good sound card, then use it to modulate the sig gen in your service monitor. Do desense test using a lossy tee like you normally would, except instead of comparing 12 dB SINAD points, you'd have to rely on listening to the repeated/decoded audio on another radio to gauge performance. To establish the baseline receiver sensitivity reference, disconnect the D-Star transmitter from the antenna system and run it into a dummy load. While listening to the repeater output on another radio, adjust sig gen output until you get clean decode sans R2D2, record the sig gen output level as the baseline. Then reconnect the transmitter to the antenna system, and repeat. If you need to increase the sig gen to get clean decode again, you have desense obviously. This isn't an ideal way to test, but it's better than nothing lacking real D-Star test equipment. Is there any way to get pre-FEC and post-FEC BER metrics out of a D-Star repeater or user radio? --- Jeff WN3A
RE: [Repeater-Builder] Desense on High Power Linear Repeater?
Aaron, My CommShop for Windows program suggests that about 88 dB of isolation is needed for a 20 watt repeater, assuming 0.2 uV sensitivity on the receiver- which you didn't specify. Bumping the power to 100 watts will increase that figure to about 95 dB. My gut feeling is that your duplexer is not up to the task. What is the model number of your Telewave duplexer, and of your Angle Linear bandpass filter? Are all of your jumpers double-shielded, with no adapters? Do you have an isolator on the output jack of your TE amplifier? Have you verified with a spectrum analyzer that your PA output is free of spurs? Since increasing the power output of a repeater seldom increases its coverage area, is it really necessary that you run 100 watts? 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of atms169 Sent: Wednesday, May 20, 2009 4:21 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense on High Power Linear Repeater? Hello everyone, I have an issue and I thought I would throw it out there! I have a Dstar VHF repeater system. A 4 Can Telewave Duplexer A Chip Angle Band Pass Filter on receive and a Chip Angle 18 dB pre-amp. Everything works just fine running the repeater barefoot at 20 watts. My problem is when I add the TE Systems amp (Around 100 watts out when hooked up), I lose the sensitivity on the receive. Our portables basically get the bad end of it. How do I go about fixing this issue so I can have the best of both worlds? I good receive and transmit? Aaron KE5KAF
Re: [Repeater-Builder] Desense on High Power Linear Repeater?
This leads me to a question that I have had on my mind. How are people doing desense testing with D-Star systems? (Remember, it's digital.) 73, Joe, K1ike Eric Lemmon wrote: Aaron, My CommShop for Windows program suggests that about 88 dB of isolation is needed for a 20 watt repeater, assuming 0.2 uV sensitivity on the receiver- which you didn't specify.
Re: [Repeater-Builder] desense question
--- On Sat, 5/2/09, va...@securenet.net va...@securenet.net wrote: From: va...@securenet.net va...@securenet.net Subject: [Repeater-Builder] desense question To: Repeater-Builder@yahoogroups.com Date: Saturday, May 2, 2009, 7:44 PM Running the hamtronics REP-200 with the optional 15 watt PA in it. After all the filtering, I get a whopping 8 watts out. I put a small strip amp inline with the TX port of the repeater, before the filtering, and it caused desense. Maybe tossing spurs - I have no way to test. Location is also not great for the moment, and the antenna is very temporary. A Diamond x500 connected with COAX (please dont shoot me). The club antenna will be down off the old tower (8 bay sinclair) and I do have the heliax for it. The amp is a UHF PA off a mobile rig, and I needed about 50 feet of RG58U to attenuate the signal from the repeater into the amp module. Is this my problem? Lack of shielding causing desense? When I put everything back to normal, my test station was solid copy. What is my best option to get a little more oomph on the output with out tossing megabucks at it? Thanks Ian VA2IR It is probably that 50 feet of rg-58. I have seen desense with as little as 6 feet of rg8 going from a transmitter to the duplexer. You may be able to bypass the amp section of the Hamtronics or just build an atuenuator in a shielded box out of resistors. Guess that you may be able to wrap the rg58 in some tinfoil and see if that helps with the desense. Not a very good longterm solution, but a way to run a check.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Yep. but there's no silver. This is (was) copper-clad aluminum. Mike WM4B _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Kris Kirby Sent: Thursday, October 09, 2008 4:50 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables On Wed, 8 Oct 2008, Mike Besemer (WM4B) wrote: These babies are looking pretty rough, Paul (et al). After one pass with the synthetic steel wool and a wipe with isopropyl alcohol, I can see that the copper plating near the open end of the outer tubes is nearly gone on two of the cans. Have not done the other two yet, but they seem to be in better shape. I'm thinking more and more they're gonna need a refurb, although I can't see how they'd do anything with these, since the don't come apart any further. Or course, silver oxide is conductive, unlike most other oxides. -- Kris Kirby, KE4AHR [EMAIL PROTECTED] mailto:kris%40catonic.us us But remember, with no superpowers comes no responsibility. --rly
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, OK, that makes sense re the 004/005 markings. And OK on the knobs. That really messed with me at first. I thought they were glued or something. It was only when I tried heating one to see if the glue would soften that I found out it was solder! I didn't have any trouble with the top of the inner tube catching on the finger stock when I put them back in, but it was a real close fit getting them in without that happening. On each cavity there were, as I recall, two or three fingers that were sprung inward a little more than the others, possibly having to do with the ends of the two coil springs putting extra pressure on them. Those were the ones I had to watch closely. As long as it hasn't compromised the solder bond of the finger stock in some way, I'm not sure the worn copper plating will do much harm. Of course if the copper plate between the finger stock solder and the inside of the fixed inner tube has deteriorated in any way (which you can't possibly determine by looking), then that would be a serious issue. My guess is it's probably OK. I would just clean them up as best I could and try it. If you can't find someone who knows where the 004 and 005 loops go, I would try an experiment. I would put both 004 on one side of the duplexer, both 005 on the other side. I would then tune it up for high pass on the 004 side (low on the 005) and make a note of the performance measurements (notch depth, insertion loss, VSWR or return loss - measure all parameters on both low and high pass sides of course). Then I would retune it so the 004 side was low pass (and 005 side high pass) and measure the performance again. If there was any difference, I'd go with the configuration that produced the better numbers. If you try this, I would be interested in what you find out. Having said all that, it's also possible the loops were intended to go the way you found them... one 004 and one 005 on each side. That wouldn't be my first guess, but it's possible. It might have something to do with making the impedances look a little nicer or some such... Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I just noticed that what I wrote here was backwards... the 004s had the strap all the way around and the 005s had the wire extension. If I figure out what goes where, I'll let you know. Did you have trouble with the top of the inner loop catching on the fingerstock and tweaking it a bit? I bent a couple of mine, but it tweaked back into place okay. Mike WM4B
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
On Wed, 8 Oct 2008, Mike Besemer (WM4B) wrote: These babies are looking pretty rough, Paul (et al). After one pass with the synthetic steel wool and a wipe with isopropyl alcohol, I can see that the copper plating near the open end of the outer tubes is nearly gone on two of the cans. Have not done the other two yet, but they seem to be in better shape. I'm thinking more and more they're gonna need a refurb, although I can't see how they'd do anything with these, since the don't come apart any further. Or course, silver oxide is conductive, unlike most other oxides. -- Kris Kirby, KE4AHR [EMAIL PROTECTED] But remember, with no superpowers comes no responsibility. --rly
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Thanks Paul. I agree with you on everything you said. One thing is for sure, I can't possibly make matters worse! I finally got to talk to a guy at dbSpectra today. He vaguely remembered the different loops but couldn't remember how they were installed. He was going to try to find some old tech data and send it to me. I haven't seen it yet, but hopefully it's coming. I'll try to take notes and pictures as I go along and send you anything that might be useful for your 'how-to' guide. 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Thursday, October 09, 2008 7:20 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, OK, that makes sense re the 004/005 markings. And OK on the knobs. That really messed with me at first. I thought they were glued or something. It was only when I tried heating one to see if the glue would soften that I found out it was solder! I didn't have any trouble with the top of the inner tube catching on the finger stock when I put them back in, but it was a real close fit getting them in without that happening. On each cavity there were, as I recall, two or three fingers that were sprung inward a little more than the others, possibly having to do with the ends of the two coil springs putting extra pressure on them. Those were the ones I had to watch closely. As long as it hasn't compromised the solder bond of the finger stock in some way, I'm not sure the worn copper plating will do much harm. Of course if the copper plate between the finger stock solder and the inside of the fixed inner tube has deteriorated in any way (which you can't possibly determine by looking), then that would be a serious issue. My guess is it's probably OK. I would just clean them up as best I could and try it. If you can't find someone who knows where the 004 and 005 loops go, I would try an experiment. I would put both 004 on one side of the duplexer, both 005 on the other side. I would then tune it up for high pass on the 004 side (low on the 005) and make a note of the performance measurements (notch depth, insertion loss, VSWR or return loss - measure all parameters on both low and high pass sides of course). Then I would retune it so the 004 side was low pass (and 005 side high pass) and measure the performance again. If there was any difference, I'd go with the configuration that produced the better numbers. If you try this, I would be interested in what you find out. Having said all that, it's also possible the loops were intended to go the way you found them... one 004 and one 005 on each side. That wouldn't be my first guess, but it's possible. It might have something to do with making the impedances look a little nicer or some such... Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I just noticed that what I wrote here was backwards... the 004s had the strap all the way around and the 005s had the wire extension. If I figure out what goes where, I'll let you know. Did you have trouble with the top of the inner loop catching on the fingerstock and tweaking it a bit? I bent a couple of mine, but it tweaked back into place okay. Mike WM4B image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Yep. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 11:35 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Hi Mike, I am a little confused as to how you are coupling the signal generator to the receiver. When you have the tx and rx connected to the duplexer normally and a dummy load on the output T (that would normally feed the antenna line) how are you coupling the signal generator to the receiver? Are you using an isolated T in the receive line to couple the generator in? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 8:21 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Gary, At this juncture, I'm not getting scientific about the actual desense measurement, but I can tell you it's in the ten's of dBs. At this point, I'm using Kevin's method. signal generator connected to the cans with the cans connected to the repeater normally. I set the signal generator to the point that the squelch breaks and turn the transmitter on manually. If the signal stays there. I'm happy (at this point). If not. I increase signal generator level until I keep the signal with the transmitter on. As I said. it's ten's of dBs at this point You're correct about where I'm connecting the dummy load. Again. I'm not using ANY antennas at this point. All testing is done into the -8920 and/or the dummy load. I'm confused about your last statement. I've not put a load at the end of the tee that feeds the feedline. If I do that, I can't feed signal to the receiver. If I take the TX line off the tee and put a dummy load there, there is no desense. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 8:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
At 10/7/2008 03:03, you wrote: With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. Make sure there's an isolator on the TX. I've seen severe desense using a perfectly good, tuned duplexer because the TX didn't like the high reactance at the notch frequency, causing a lot of broadband noise to come out of the PA. If the 8920 is full duplex, I'd try a dummy load on a coupler or sampler instead just to make sure there isn't something inside it that's generating the noise. Bob NO6B
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Just out of curiosity what power supply are you using? I've seen a fair amount of RFI from the Astron SS series.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. You lost me on that one. You're saying you're testing for desense by removing the tee from the antenna port of the duplexer, feeding the Tx leg of the duplexer into a dummy load, and the Rx leg gets fed by your 8920 sig gen? If that's the case, then that's not much of a test since you're no longer duplexing. You've totally isolated the Tx and Rx, so all you really know is whether or not you have in-cabinet desense (i.e. between the transmitter and receiver internally due to poor shielding or cable cross-coupling). Or maybe I'm totally misunderstanding how you're doing the desense test - if I have, please re-explain. The easiest way to do the desense test (while keeping the feedline and antenna out of the equation) is to connect the duplexer antenna port to a high-quality (low-noise) dummy load, with an iso-tee inline between the duplexer and load. Connect your 8920 sig gen to the decoupled port on the iso-tee, generate a weak signal while monitoring the repeater Rx local receiver, and key the transmitter on and off manually. If you have desense at that point, and it sounds ratty as if something is breaking down or making intermittant contact, then go do your tappin' n' wigglin' to see if you can narrow down the list of suspects. The dummy load on the 8920 RF port is OK, but I'd still be more comfortable using a good external load and isotee. Intermittant desense can sometimes be traced back to a component or solder joint in the transmitter being defective, which can manifest as arcing (however microscopic). The resulting transmitter noise may not be easily discernable on a spectrum analyzer, especially without attenuation of the carrier frequency to increase the dynamic range of the test equipment, but may still cause appreciable desense due to the broadband noise falling on the Rx frequency. Yes, half of the duplexer's job is to attenuate transmitter noise to keep it from getting to the receiver, but if a failing component causes the effective noise level to be elevated 20 or 30 dB, that's 20 or 30 dB more isolation your duplexer would need to provide to prevent desense, and often that kind of headroom doesn't exist. Have you measured the isolation of your duplexer from Tx port to Rx port with the antenna port terminated in a dummy load? What is the measured isolation at the Tx and Rx frequencies doing this test? --- Jeff WN3A
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Jeff, I have been watching this thread and must say your explanation here is very well done. Thank you from the rest of us watching. Collin -Original Message- From: Jeff DePolo [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wed, 8 Oct 2008 1:00 pm Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. You lost me on that one. You're saying you're testing for desense by removing the tee from the antenna port of the duplexer, feeding the Tx leg of the duplexer into a dummy load, and the Rx leg gets fed by your 8920 sig gen? If that's the case, then that's not much of a test since you're no longer duplexing. You've totally isolated the Tx and Rx, so all you really know is whether or not you have in-cabinet desense (i.e. between the transmitter and receiver internally due to poor shielding or cable cross-coupling). Or maybe I'm totally misunderstanding how you're doing the desense test - if I have, please re-explain. The easiest way to do the desense test (while keeping the feedline and antenna out of the equation) is to connect the duplexer antenna port to a high-quality (low-noise) dummy load, with an iso-tee inline between the duplexer and load. Connect your 8920 sig gen to the decoupled port on the iso-tee, generate a weak signal while monitoring the repeater Rx local receiver, and key the transmitter on and off manually. If you have desense at that point, and it sounds ratty as if something is breaking down or making intermittant contact, then go do your tappin' n' wigglin' to see if you can narrow down the list of suspects. The dummy load on the 8920 RF port is OK, but I'd still be more comfortable using a good external load and isotee. Intermittant desense can sometimes be traced back to a component or solder joint in the transmitter being defective, which can manifest as arcing (however microscopic). The resulting transmitter noise may not be easily discernable on a spectrum analyzer, especially without attenuation of the carrier frequency to increase the dynamic range of the test equipment, but may still cause appreciable desense due to the broadband noise falling on the Rx frequency. Yes, half of the duplexer's job is to attenuate transmitter noise to keep it from getting to the receiver, but if a failing component causes the effective noise level to be elevated 20 or 30 dB, that's 20 or 30 dB more isolation your duplexer would need to provide to prevent desense, and often that kind of headroom doesn't exist. Have you measured the isolation of your duplexer from Tx port to Rx port with the antenna port terminated in a dummy load? What is the measured isolation at the Tx and Rx frequencies doing this test? --- Jeff WN3A
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
It's an analog supply built into the repeater. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Wednesday, October 08, 2008 11:55 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Just out of curiosity what power supply are you using? I've seen a fair amount of RFI from the Astron SS series. image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Tuesday, October 07, 2008 6:03 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, I can hear the fingerstock scraping against the inner tube... not a BAD scraping... just what sounds like good metal-to-metal contact. That is normal. The reason I asked is mine had stopped making that noise. It was almost completely silent when I rotated the knobs. That was one of the major things that led me to conclude something was really wrong inside. I knew silence when being tuned wasn't normal for those cans. After being refurbished it is back to making a healthy scraping sound. I was also thinking about cleaning the mating surfaces on the top... just need to get the gumption to do it. I'm getting tired of having my butt kicked! I know that feeling! I cleaned *every* mating surface while I had them apart, corrected some manufacturing sloppiness, and made a minor modification (which, I'm sure, was totally unnecessary, but I wasn't leaving any stone unturned). Good luck! 73, Paul N1BUG image001.jpgimage002.jpg
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes… looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white ‘stuff’ growing in there… have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed… a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is… which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Paul, I just noticed that what I wrote here was backwards... the 004s had the strap all the way around and the 005s had the wire extension. If I figure out what goes where, I'll let you know. Did you have trouble with the top of the inner loop catching on the fingerstock and tweaking it a bit? I bent a couple of mine, but it tweaked back into place okay. Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Forgot to mention... yes, the knobs were soldered on. I'm amazed they take that much heat without damage. I'm glad you figured that part out... it had me stumped. I'll report back with progress when I get them done. 73, Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
These babies are looking pretty rough, Paul (et al). After one pass with the synthetic steel wool and a wipe with isopropyl alcohol, I can see that the copper plating near the open end of the outer tubes is nearly gone on two of the cans. Have not done the other two yet, but they seem to be in better shape. I'm thinking more and more they're gonna need a refurb, although I can't see how they'd do anything with these, since the don't come apart any further. Anybody ever done a refurb from dbSpectra? Wish they'd return my calls/emails. Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs.
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike Besemer (WM4B) wrote: I have a strange feeling that it’s arching around the fingerstock. The inner tuning tubes showed definite signs of wear, but I THOUGHT the fingerstock was making good contact. Is there any ‘approved’ conductive lubricant for that area? Your problem sounds a lot like the trouble I was having with my DB4062 (the 6 cavity version of the 4060). I would get it tuned and think all was well, only to have major desense the next day. It nearly drove me nuts! What happens desense-wise if you tap lightly on the big tuning knobs while the transmitter is running? Do the cans make a nice scraping sound when you turn the knobs during tune up? Mine had the moving part of the center conductor and the finger stock coated with some kind of lubricant, which had partially dried up and was interfering with contact. Check the coil springs around the finger stock to make sure they are applying adequate pressure and are not stretched out. I also recommend you check and clean EVERY metal to metal mating surface, including where the box containing the coupling loop bolts to the cavity top. I wrote up something (incomplete) on my restoration project, which can be found here: http://www.repeater.n1bug.com/duplexerrefurb.html I think Mike Morris was going to put this on the repeater-builder site, but I don't see it there yet or I'd have given that link instead. (Mike Morris: I can supply a version of this minus the DHTML menu etc. if you want it) Almost one year since the restoration now and all's well... 73, Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs. image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
No worries, Eric. I'm not giving up yet! I just want to be able to offer the answer to the inevitable 'worst case scenario' question. I definitely agree with you though. I'm a newbie to repeater stuff, but I've been juggling electrons for a long time and know that sometimes you've got to walk away for a while and get a new perspective. Having this mailing list is a huge advantage to guys like me who are just trying to 'get it done' to keep the membership happy! As always, I appreciate you (and everyone else's) advice. I've learned a lot just lurking on the list and even more when I took on the project of building this 'Frankenrepeater' project. I'm definitely just about out of ideas though. read all I can find here, on the website, and everyplace else I can think of and am running out of ideas. I guess I need to take the cans apart and inspect them again and also swap in the spare notch capacitors. but beyond that I'm getting to be at a loss! 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Eric Lemmon Sent: Monday, October 06, 2008 10:50 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, I urge you to avoid jumping to any conclusions, before you determine the cause of the problem. With all due respect, I think it is premature to condemn any component of your repeater until you have performed a very thorough and intelligent investigation. The worst thing you can do, in my opinion, is rush to a conclusion simply because non-technical people want an immediate answer. Tell 'em to wait! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I've got a club meeting Thursday and need to present something to the club. Assuming worse case that the cans I have are a total loss, what suggestions have ya'll got for a replacement, assuming a 30 watt transmitter (our old reliable Mark 4). Does anybody offer a discount to hams? Any reasonable chance of getting the cans I've got repaired? Mike WM4B image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Paul, I've been thinking the same thing. I hate to tear them apart again, but I want to clean the metal-to-metal surfaces again. I can hear the fingerstock scraping against the inner tube... not a BAD scraping... just what sounds like good metal-to-metal contact. I was also thinking about cleaning the mating surfaces on the top... just need to get the gumption to do it. I'm getting tired of having my butt kicked! Thanks es 73, Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Tuesday, October 07, 2008 6:58 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike Besemer (WM4B) wrote: I have a strange feeling that it's arching around the fingerstock. The inner tuning tubes showed definite signs of wear, but I THOUGHT the fingerstock was making good contact. Is there any 'approved' conductive lubricant for that area? Your problem sounds a lot like the trouble I was having with my DB4062 (the 6 cavity version of the 4060). I would get it tuned and think all was well, only to have major desense the next day. It nearly drove me nuts! What happens desense-wise if you tap lightly on the big tuning knobs while the transmitter is running? Do the cans make a nice scraping sound when you turn the knobs during tune up? Mine had the moving part of the center conductor and the finger stock coated with some kind of lubricant, which had partially dried up and was interfering with contact. Check the coil springs around the finger stock to make sure they are applying adequate pressure and are not stretched out. I also recommend you check and clean EVERY metal to metal mating surface, including where the box containing the coupling loop bolts to the cavity top. I wrote up something (incomplete) on my restoration project, which can be found here: http://www.repeater.n1bug.com/duplexerrefurb.html I think Mike Morris was going to put this on the repeater-builder site, but I don't see it there yet or I'd have given that link instead. (Mike Morris: I can supply a version of this minus the DHTML menu etc. if you want it) Almost one year since the restoration now and all's well... 73, Paul N1BUG Yahoo! Groups Links
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I've never worked with cans or repeaters, but I've witnessed similar issues caused by oxidation/corrosion. Have you tried using a conductive grease on the housing joints and the rods? It appears silver-based grease is suggested for all applications above 50 mhz. Good luck! Jacob Suter (unlicensed newb) From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Okay. I got the cable dilemma sorted out thanks to some photos I'd taken earlier, but I CANNOT get the desense out of these things. Some history: The cans and the repeater were both in storage for several years. We got a 'too good to be true' deal on the site and I pulled everything out of storage. The repeater (Mark 4) and cans were both originally on 146.85. The repeater was brought back to life on 145.11 and I tuned the cans using an HP-8920A. When I was done, I had no detectable desense either into the -8920A or at the site. Fast forward 2 months. The repeater goes deaf. I make a trip to the site (about 40 minutes) and find terrible desense. I blamed the service technician who'd just installed a new repeater for the BoE at the site, tweaked up the cans and everything was fine. for about a day. The repeater sounded great and the sensitivity was fine, but it had a terrible noise on transmit after it had been at rest for a while. About 2 minutes of RF would clean it up and it would work fine until it rested again for about 40 minutes. then it all started over again. The noise was only when the squelch was open. ID's and announcements were fine. (AH-HA!) I finally got a chance to make the trip back to the site and pulled everything home with me. I took a look at the repeater, just to give it a clean bill of health. It all looked good. I made only a few minor tweaks. The cans were noisy. I could turn the bandpass screws and I'd get noise on the receiver. That's what led me to pull the cans apart (below) to inspect and clean. There was some growth on the copper further up the outer tube, but nothing by the fingerstock. I have it a nice vinegar bath and cleaned it with a paint roller stuck inside the outer tube. It cleaned up nicely and I gave it a nice bath with the garden hose and baked the whole thing in the oven until it was good and dry. The entire process was repeated for each can. The enclosure with the notch capacitor was removed for this process, and the tuning rod screws were removed from the top to let the tuning rod drop down so I could get into the outer tube. After I put it all back together, I checked the fingerstock and it all looked good. Initial tuneup with the HP-8920 went fine and I soon had the repeater running through the cans into the -8920, breaking the squelch at about -116 dB with no detectable desense. Then. I went to bed. The next day, the desense was back with a vengeance. Been tuning for 2 days now (I thought I found it last night when I found a connector spinning on one of the cables going to the T-connector) and I CANNOT get rid of it. Sometimes it sounds like an AM radio driving under a power line. sometimes it just crackles. It's got to be microarcing somewhere, but I HATE taking those cavities apart again. (BTW, the cable with the spinning connector was replaced with good, MILSPEC RG-214 and MILSPEC connectors.) Have I missed anything? I'm really starting to think that these things are beyond salvage, but I sure hate to break that news to the club! Help! 73, Mike WM4B
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, I can hear the fingerstock scraping against the inner tube... not a BAD scraping... just what sounds like good metal-to-metal contact. That is normal. The reason I asked is mine had stopped making that noise. It was almost completely silent when I rotated the knobs. That was one of the major things that led me to conclude something was really wrong inside. I knew silence when being tuned wasn't normal for those cans. After being refurbished it is back to making a healthy scraping sound. I was also thinking about cleaning the mating surfaces on the top... just need to get the gumption to do it. I'm getting tired of having my butt kicked! I know that feeling! I cleaned *every* mating surface while I had them apart, corrected some manufacturing sloppiness, and made a minor modification (which, I'm sure, was totally unnecessary, but I wasn't leaving any stone unturned). Good luck! 73, Paul N1BUG
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
While we are on the subject of the DB4060/62, I've got a couple of dead cans with a bad tuning cap. Does anyone have a source I can call to buy some of the Johanson 5602 tuning caps? Some of the Johanson distributors don't stock it and require a big min order. I've looked at Nebraska Surplus and they have some that might work, but I'd like to find the exact replacement if possible. Thanks, Ralph W4XE
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Gary, At this juncture, I'm not getting scientific about the actual desense measurement, but I can tell you it's in the ten's of dBs. At this point, I'm using Kevin's method. signal generator connected to the cans with the cans connected to the repeater normally. I set the signal generator to the point that the squelch breaks and turn the transmitter on manually. If the signal stays there. I'm happy (at this point). If not. I increase signal generator level until I keep the signal with the transmitter on. As I said. it's ten's of dBs at this point You're correct about where I'm connecting the dummy load. Again. I'm not using ANY antennas at this point. All testing is done into the -8920 and/or the dummy load. I'm confused about your last statement. I've not put a load at the end of the tee that feeds the feedline. If I do that, I can't feed signal to the receiver. If I take the TX line off the tee and put a dummy load there, there is no desense. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 8:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs. image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Hi Mike, I am a little confused as to how you are coupling the signal generator to the receiver. When you have the tx and rx connected to the duplexer normally and a dummy load on the output T (that would normally feed the antenna line) how are you coupling the signal generator to the receiver? Are you using an isolated T in the receive line to couple the generator in? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 8:21 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Gary, At this juncture, I'm not getting scientific about the actual desense measurement, but I can tell you it's in the ten's of dBs. At this point, I'm using Kevin's method. signal generator connected to the cans with the cans connected to the repeater normally. I set the signal generator to the point that the squelch breaks and turn the transmitter on manually. If the signal stays there. I'm happy (at this point). If not. I increase signal generator level until I keep the signal with the transmitter on. As I said. it's ten's of dBs at this point You're correct about where I'm connecting the dummy load. Again. I'm not using ANY antennas at this point. All testing is done into the -8920 and/or the dummy load. I'm confused about your last statement. I've not put a load at the end of the tee that feeds the feedline. If I do that, I can't feed signal to the receiver. If I take the TX line off the tee and put a dummy load there, there is no desense. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 8:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Have you look at your transmitter when the desense starts? David -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Okay. I got the cable dilemma sorted out thanks to some photos I'd taken earlier, but I CANNOT get the desense out of these things. Some history: The cans and the repeater were both in storage for several years. We got a 'too good to be true' deal on the site and I pulled everything out of storage. The repeater (Mark 4) and cans were both originally on 146.85. The repeater was brought back to life on 145.11 and I tuned the cans using an HP-8920A. When I was done, I had no detectable desense either into the -8920A or at the site. Fast forward 2 months. The repeater goes deaf. I make a trip to the site (about 40 minutes) and find terrible desense. I blamed the service technician who'd just installed a new repeater for the BoE at the site, tweaked up the cans and everything was fine. for about a day. The repeater sounded great and the sensitivity was fine, but it had a terrible noise on transmit after it had been at rest for a while. About 2 minutes of RF would clean it up and it would work fine until it rested again for about 40 minutes. then it all started over again. The noise was only when the squelch was open. ID's and announcements were fine. (AH-HA!) I finally got a chance to make the trip back to the site and pulled everything home with me. I took a look at the repeater, just to give it a clean bill of health. It all looked good. I made only a few minor tweaks. The cans were noisy. I could turn the bandpass screws and I'd get noise on the receiver. That's what led me to pull the cans apart (below) to inspect and clean. There was some growth on the copper further up the outer tube, but nothing by the fingerstock. I have it a nice vinegar bath and cleaned it with a paint roller stuck inside the outer tube. It cleaned up nicely and I gave it a nice bath with the garden hose and baked the whole thing in the oven until it was good and dry. The entire process was repeated for each can. The enclosure with the notch capacitor was removed for this process, and the tuning rod screws were removed from the top to let the tuning rod drop down so I could get into the outer tube. After I put it all back together, I checked the fingerstock and it all looked good. Initial tuneup with the HP-8920 went fine and I soon had the repeater running through the cans into the -8920, breaking the squelch at about -116 dB with no detectable desense. Then. I went to bed. The next day, the desense was back with a vengeance. Been tuning for 2 days now (I thought I found it last night when I found a connector spinning on one of the cables going to the T-connector) and I CANNOT get rid of it. Sometimes it sounds like an AM radio driving under a power line. sometimes it just crackles. It's got to be microarcing somewhere, but I HATE taking those cavities apart again. (BTW, the cable with the spinning connector was replaced with good, MILSPEC RG-214 and MILSPEC connectors.) Have I missed anything? I'm really starting to think that these things are beyond salvage, but I sure hate to break that news to the club! Help! 73, Mike WM4B _ From: Mike Besemer (WM4B) [mailto:mwbesemer@ mailto:[EMAIL PROTECTED] cox.net] Sent: Sunday, October 05, 2008 9:10 PM To: 'Repeater-Builder@yahoogroups.com' Subject: DB4060 Duplexer Cables I spent the weekend working on a set of DB4060 cans (cleaning and retuning) and have managed to commit the ultimate stupidity. I had all the harnesses off and instead of MARKING them I just laid them out on the bench. Unfortunately, the bench got 'cleaned' and the cables are now all mixed up. I can tell which 2 cables went between the cans and which went to the T-connector, but all 4-cables are different lengths. I assume that the shorter of the two cables go on the TX (high) side of the cans and the shorter go on the RX (low) side of the cans. Am I correct? Thanks for the help. next time I'll mark the cables! 73, Mike WM4B
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
David, Not sure what you're asking, but if you're asking about spurs, she's a clean as a whistle. VSWR is fine as well. Mike From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of David Murman Sent: Monday, October 06, 2008 8:51 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Have you look at your transmitter when the desense starts? David -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Okay. I got the cable dilemma sorted out thanks to some photos I'd taken earlier, but I CANNOT get the desense out of these things. Some history: The cans and the repeater were both in storage for several years. We got a 'too good to be true' deal on the site and I pulled everything out of storage. The repeater (Mark 4) and cans were both originally on 146.85. The repeater was brought back to life on 145.11 and I tuned the cans using an HP-8920A. When I was done, I had no detectable desense either into the -8920A or at the site. Fast forward 2 months. The repeater goes deaf. I make a trip to the site (about 40 minutes) and find terrible desense. I blamed the service technician who'd just installed a new repeater for the BoE at the site, tweaked up the cans and everything was fine. for about a day. The repeater sounded great and the sensitivity was fine, but it had a terrible noise on transmit after it had been at rest for a while. About 2 minutes of RF would clean it up and it would work fine until it rested again for about 40 minutes. then it all started over again. The noise was only when the squelch was open. ID's and announcements were fine. (AH-HA!) I finally got a chance to make the trip back to the site and pulled everything home with me. I took a look at the repeater, just to give it a clean bill of health. It all looked good. I made only a few minor tweaks. The cans were noisy. I could turn the bandpass screws and I'd get noise on the receiver. That's what led me to pull the cans apart (below) to inspect and clean. There was some growth on the copper further up the outer tube, but nothing by the fingerstock. I have it a nice vinegar bath and cleaned it with a paint roller stuck inside the outer tube. It cleaned up nicely and I gave it a nice bath with the garden hose and baked the whole thing in the oven until it was good and dry. The entire process was repeated for each can. The enclosure with the notch capacitor was removed for this process, and the tuning rod screws were removed from the top to let the tuning rod drop down so I could get into the outer tube. After I put it all back together, I checked the fingerstock and it all looked good. Initial tuneup with the HP-8920 went fine and I soon had the repeater running through the cans into the -8920, breaking the squelch at about -116 dB with no detectable desense. Then. I went to bed. The next day, the desense was back with a vengeance. Been tuning for 2 days now (I thought I found it last night when I found a connector spinning on one of the cables going to the T-connector) and I CANNOT get rid of it. Sometimes it sounds like an AM radio driving under a power line. sometimes it just crackles. It's got to be microarcing somewhere, but I HATE taking those cavities apart again. (BTW, the cable with the spinning connector was replaced with good, MILSPEC RG-214 and MILSPEC connectors.) Have I missed anything? I'm really starting to think that these things are beyond salvage, but I sure hate to break that news to the club! Help! 73, Mike WM4B _ From: Mike Besemer (WM4B) [mailto:[EMAIL PROTECTED] Sent: Sunday, October 05, 2008 9:10 PM To: 'Repeater-Builder@yahoogroups.com' Subject: DB4060 Duplexer Cables I spent the weekend working on a set of DB4060 cans (cleaning and retuning) and have managed to commit the ultimate stupidity. I had all the harnesses off and instead of MARKING them I just laid them out on the bench. Unfortunately, the bench got 'cleaned' and the cables are now all mixed up. I can tell which 2 cables went between the cans and which went to the T-connector, but all 4-cables are different lengths. I assume that the shorter of the two cables go on the TX (high) side of the cans and the shorter go on the RX (low) side of the cans. Am I correct? Thanks for the help. next time I'll mark the cables! 73, Mike WM4B
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I neglected to mention in the first post, but I also put the crystals into a 2nd repeater we have and had the same problem. I may have to try tuning the cans on our spare 6.85 machine. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 8:56 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables David, Not sure what youre asking, but if youre asking about spurs, shes a clean as a whistle. VSWR is fine as well. Mike From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of David Murman Sent: Monday, October 06, 2008 8:51 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Have you look at your transmitter when the desense starts? David -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Okay I got the cable dilemma sorted out thanks to some photos Id taken earlier, but I CANNOT get the desense out of these things. Some history: The cans and the repeater were both in storage for several years. We got a too good to be true deal on the site and I pulled everything out of storage. The repeater (Mark 4) and cans were both originally on 146.85. The repeater was brought back to life on 145.11 and I tuned the cans using an HP-8920A. When I was done, I had no detectable desense either into the -8920A or at the site. Fast forward 2 months. The repeater goes deaf. I make a trip to the site (about 40 minutes) and find terrible desense. I blamed the service technician whod just installed a new repeater for the BoE at the site, tweaked up the cans and everything was fine for about a day. The repeater sounded great and the sensitivity was fine, but it had a terrible noise on transmit after it had been at rest for a while. About 2 minutes of RF would clean it up and it would work fine until it rested again for about 40 minutes then it all started over again. The noise was only when the squelch was open IDs and announcements were fine. (AH-HA!) I finally got a chance to make the trip back to the site and pulled everything home with me. I took a look at the repeater, just to give it a clean bill of health. It all looked good I made only a few minor tweaks. The cans were noisy. I could turn the bandpass screws and Id get noise on the receiver. Thats what led me to pull the cans apart (below) to inspect and clean. There was some growth on the copper further up the outer tube, but nothing by the fingerstock. I have it a nice vinegar bath and cleaned it with a paint roller stuck inside the outer tube. It cleaned up nicely and I gave it a nice bath with the garden hose and baked the whole thing in the oven until it was good and dry. The entire process was repeated for each can. The enclosure with the notch capacitor was removed for this process, and the tuning rod screws were removed from the top to let the tuning rod drop down so I could get into the outer tube. After I put it all back together, I checked the fingerstock and it all looked good. Initial tuneup with the HP-8920 went fine and I soon had the repeater running through the cans into the -8920, breaking the squelch at about -116 dB with no detectable desense. Then I went to bed. The next day, the desense was back with a vengeance. Been tuning for 2 days now (I thought I found it last night when I found a connector spinning on one of the cables going to the T-connector) and I CANNOT get rid of it. Sometimes it sounds like an AM radio driving under a power line sometimes it just crackles. Its got to be microarcing somewhere, but I HATE taking those cavities apart again. (BTW, the cable with the spinning connector was replaced with good, MILSPEC RG-214 and MILSPEC connectors.) Have I missed anything? Im really starting to think that these things are beyond salvage, but I sure hate to break that news to the club! Help! 73, Mike WM4B _ From: Mike Besemer (WM4B) [mailto:[EMAIL PROTECTED] Sent: Sunday, October 05, 2008 9:10 PM To: 'Repeater-Builder@yahoogroups.com' Subject: DB4060 Duplexer Cables I spent the weekend working on a set of DB4060 cans (cleaning and retuning) and have managed to commit the ultimate stupidity. I had all the harnesses off and instead of MARKING them I just laid them out on the bench. Unfortunately, the bench got cleaned and the cables are now all mixed up. I can tell which 2 cables went between the cans and which went to the T-connector, but all 4-cables are different lengths. I assume
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Sounds like maybe a bad notch cap or a bad harness cable. At first I thought maybe a transmitter spur, but you've now ruled that out. Neither may show up on your HP, but under real power it could. Chuck WB2EDV - Original Message - From: Mike Besemer (WM4B) [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, October 06, 2008 9:04 PM Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I neglected to mention in the first post, but I also put the crystals into a 2nd repeater we have and had the same problem. I may have to try tuning the cans on our spare 6.85 machine. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 8:56 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables David, Not sure what you're asking, but if you're asking about spurs, she's a clean as a whistle. VSWR is fine as well. Mike
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I don't THINK it's a cable. no amount of beating, poking, or flexing seems to make any difference. I've thought about the notch caps. I do have a couple of spares. maybe I'll try to swap them in. The question is. WHICH TWO? I've swapped TX and RX sides of the duplexers already with no effect. You'd think that the notch caps on the RX side would be the ones that'd cause the most grief, but I can see how the others would too. Either way, I'd have expected to see some difference when I swapped TX and RX sides. I have a strange feeling that it's arching around the fingerstock. The inner tuning tubes showed definite signs of wear, but I THOUGHT the fingerstock was making good contact. Is there any 'approved' conductive lubricant for that area? Mike WM4B _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Kelsey Sent: Monday, October 06, 2008 9:15 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Sounds like maybe a bad notch cap or a bad harness cable. At first I thought maybe a transmitter spur, but you've now ruled that out. Neither may show up on your HP, but under real power it could. Chuck WB2EDV - Original Message - From: Mike Besemer (WM4B) [EMAIL PROTECTED] mailto:mwbesemer%40cox.net net To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Sent: Monday, October 06, 2008 9:04 PM Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I neglected to mention in the first post, but I also put the crystals into a 2nd repeater we have and had the same problem. I may have to try tuning the cans on our spare 6.85 machine. Mike WM4B From: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com [mailto:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 8:56 PM To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables David, Not sure what you're asking, but if you're asking about spurs, she's a clean as a whistle. VSWR is fine as well. Mike
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I've got a club meeting Thursday and need to present something to the club. Assuming worse case that the cans I have are a total loss, what suggestions have ya'll got for a replacement, assuming a 30 watt transmitter (our old reliable Mark 4). Does anybody offer a discount to hams? Any reasonable chance of getting the cans I've got repaired? Mike WM4B _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Kelsey Sent: Monday, October 06, 2008 9:15 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Sounds like maybe a bad notch cap or a bad harness cable. At first I thought maybe a transmitter spur, but you've now ruled that out. Neither may show up on your HP, but under real power it could. Chuck WB2EDV - Original Message - From: Mike Besemer (WM4B) [EMAIL PROTECTED] mailto:mwbesemer%40cox.net net To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Sent: Monday, October 06, 2008 9:04 PM Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I neglected to mention in the first post, but I also put the crystals into a 2nd repeater we have and had the same problem. I may have to try tuning the cans on our spare 6.85 machine. Mike WM4B From: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com [mailto:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 8:56 PM To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables David, Not sure what you're asking, but if you're asking about spurs, she's a clean as a whistle. VSWR is fine as well. Mike
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, I urge you to avoid jumping to any conclusions, before you determine the cause of the problem. With all due respect, I think it is premature to condemn any component of your repeater until you have performed a very thorough and intelligent investigation. The worst thing you can do, in my opinion, is rush to a conclusion simply because non-technical people want an immediate answer. Tell 'em to wait! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I've got a club meeting Thursday and need to present something to the club. Assuming worse case that the cans I have are a total loss, what suggestions have ya'll got for a replacement, assuming a 30 watt transmitter (our old reliable Mark 4). Does anybody offer a discount to hams? Any reasonable chance of getting the cans I've got repaired? Mike WM4B
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
How are you checking for desense? Are you using an isolated T between the duplexer and antenna line and doing the same when measuring desense on the dummy load? Are you measuring site noise? Do this the same way you would measure desense with the isolated T in the line. But first see what the receiver sensitivity is with the dummy load connected in place of the antenna. Then replace the dummy load with the antenna, do not key the transmitter, and measure the difference in receiver with the antenna connected verses the dummy load. With TV stations present you may be surprised at the amount of site noise present. Then key the transmitter and again measure receiver sensitivity thru the isolated T. If you haven't done this you may find that a lot of the problem is site noise rather than desense problems. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Stu Benner Sent: Friday, January 25, 2008 12:52 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense Problem on 222 MHz Repeater Our group has substantial technical knowledge and experience, but we've been just about beaten down by a problem with our repeater. A brief overview of our situation follows. We have a 222 MHz repeater comprised of a converted Micor mobile, Telewave TPRD-2254 BpBr duplexer, AM-6155 PA modified for class C operation at 250W, and a DB-264JJ antenna at 80 ft. fed by 1/2' Heliax on a commercial FM broadcast tower . With the duplexer terminated into a load, we have about 1 dB degradation in sensitivity when transmitting. However, with the antenna connected to the duplexer, we experience in excess 15 dB of desensitization. We have eliminated other narrowband transmitters and analog TV transmitters as contributing factors. We are left with a channel 12 digital TV transmitter at an adjacent site as a key contributor to the problem. Our hypothesis is that we have broadband IMD products from the mix of our transmitter and the DTV transmitter that are appearing in and near our receiver passband. Is it a rusty bolt problem or is there some other non-linear component somewhere on the site or in our system that is the mixing point - we don't know. I'd be interested in beginning a dialog with anyone who might be able to give us some further insight into this problem. Regards, Stu Benner W3STU Boonsboro, MD
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
Just make sure to pull the unused loop out of the cavity. Steve / K6SCA Gary Schafer [EMAIL PROTECTED] wrote: If you have an extra band pass cavity then you also have a notch cavity. Just connect a T to one port of the band pass cavity and ignore the other port on the cavity. This will work as a notch cavity for your testing. 73 Gary K4FMX - From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Stu Benner Sent: Friday, January 25, 2008 4:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater Thanks to everyone for the replies so far. Please see comments embedded below. I think that they address most of the comments, questions, and recommendations posed by all to this point. If you suspect IMD between the channel 12 DTV transmitter and your Tx carrier, work on attenuating the DTV signal. Using cavity notch filters to reject the entire 6 MHz of DTV isn't too practical, so instead, try adding pass cavities on your Tx before the duplexer input. That will help determine if the IM is originating in your PA. An isolator *may* help, but with channel 12 being the better part of 20 MHz away (about 10%), it may not afford full protection -- isolators don't have infinite bandwidth. Likewise, finding a 250 watt 220 MHz isolator may not be easy. I think I have some 220 isolators that came off a combiner (Sinclair), but doubt they're good for 250 watts judging by their size. [Stu] Agree, notches don't work well for that plus we don't have handy any cavities that will tune there. Have used up to two BP cavities in the TX path along with a 2-stage isolator. No difference in desense is observed. If you suspect a rusty bolt mix, use an alternate antenna for testing. If nothing else, try a quarter-wave whip (suitable for operation at your 250 watts TPO), even if it's just temporarily mounted on the tower (be sure it's at a sufficient height to prevent desense due to close proximity to the repeater itself). [Stu] We're presently on split antennas. One is at about 80 ft., the other is at about 15 ft. This improves the desense on the order of 6 dB. Another good possibility is IM in your receiver front end (or preamp, if you're using one). Again, pass cavities are your friend here. Attenuate the channel 12 signal as much as possible and see if it makes a difference. Have you looked at what sigs are reaching your receiver input on a spectrum analyzer? With 15 dB of desense, you should be able to see the culprit(s); it's not like they're going to be buried in the noise if it's causing 15 dB of desense. [Stu] The desense is significant with or without a preamp. Worse with but I can't find my notes to quote numbers. Used up to 2 BP cavities on RX with no perceptable difference in desense. Have also installed a DCI 4-pole filter on RX and TX with no effect. Have looked at the receiver input with a spectrum analyzer. The most significant signal is the one FM broadcast transmitter at the site. Running power down on it or turning it off has no effect on the desense. Our TX signal at our RX input is consistent with our measured duplexer isolation (about -88 dBc or -34 dBm). Within several hundred kHz of the RX frequency there are no detectable narrowband signals. Even that 1 dB of desense would give me some agita. I'd verify that the duplexers are properly tuned and the transmitter is clean before even starting down any other paths related to the channel 12 issue. IIRC, the Telewave cavities have adjustable coupling. If necessary, sacrifice a little extra loss for additional rejection if necessary. [Stu] I tuned the duplexer myself with a network analyzer and the transmitter looks clean. I have coupling set where I get about 1 dB through loss and the notches are at about 88 dB on TX and about 90 dB on RX. I also assume you're using all known-good interconnect cables (no foil+braid or other cables not suitable for duplex operation). [Stu] All cables are either Heliax or double braided. Are you using a Polyphaser or other type of surge arrestor? If so, try bypassing it. I've seen gas discharge tube type surge arrestors become noisemakers after absorbing a strike. [Stu] Yes but there is no difference in desense when it is removed. Has the VSWR changed at all on your antenna? If so, it could indicate water in a connector or the harness which will cause all kinds of grief, including wideband noise. [Stu] The problem has existed since the repeater was installed. It exists whether we duplex on a DB264 at 80 feet or a G7-220 at 15 feet, both fed with Heliax Finally, does the desense change appreciably if you vary transmitter power output (it probably will). Do you any have desense when running on just exciter power? [Stu] The desense is roughly proportional to transmit power. Barely perceptable at 20W (exciter only
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
If you have an extra band pass cavity then you also have a notch cavity. Just connect a T to one port of the band pass cavity and ignore the other port on the cavity. This will work as a notch cavity for your testing. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Stu Benner Sent: Friday, January 25, 2008 4:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater Thanks to everyone for the replies so far. Please see comments embedded below. I think that they address most of the comments, questions, and recommendations posed by all to this point. If you suspect IMD between the channel 12 DTV transmitter and your Tx carrier, work on attenuating the DTV signal. Using cavity notch filters to reject the entire 6 MHz of DTV isn't too practical, so instead, try adding pass cavities on your Tx before the duplexer input. That will help determine if the IM is originating in your PA. An isolator *may* help, but with channel 12 being the better part of 20 MHz away (about 10%), it may not afford full protection -- isolators don't have infinite bandwidth. Likewise, finding a 250 watt 220 MHz isolator may not be easy. I think I have some 220 isolators that came off a combiner (Sinclair), but doubt they're good for 250 watts judging by their size. [Stu] Agree, notches don't work well for that plus we don't have handy any cavities that will tune there. Have used up to two BP cavities in the TX path along with a 2-stage isolator. No difference in desense is observed. If you suspect a rusty bolt mix, use an alternate antenna for testing. If nothing else, try a quarter-wave whip (suitable for operation at your 250 watts TPO), even if it's just temporarily mounted on the tower (be sure it's at a sufficient height to prevent desense due to close proximity to the repeater itself). [Stu] We're presently on split antennas. One is at about 80 ft., the other is at about 15 ft. This improves the desense on the order of 6 dB. Another good possibility is IM in your receiver front end (or preamp, if you're using one). Again, pass cavities are your friend here. Attenuate the channel 12 signal as much as possible and see if it makes a difference. Have you looked at what sigs are reaching your receiver input on a spectrum analyzer? With 15 dB of desense, you should be able to see the culprit(s); it's not like they're going to be buried in the noise if it's causing 15 dB of desense. [Stu] The desense is significant with or without a preamp. Worse with but I can't find my notes to quote numbers. Used up to 2 BP cavities on RX with no perceptable difference in desense. Have also installed a DCI 4-pole filter on RX and TX with no effect. Have looked at the receiver input with a spectrum analyzer. The most significant signal is the one FM broadcast transmitter at the site. Running power down on it or turning it off has no effect on the desense. Our TX signal at our RX input is consistent with our measured duplexer isolation (about -88 dBc or -34 dBm). Within several hundred kHz of the RX frequency there are no detectable narrowband signals. Even that 1 dB of desense would give me some agita. I'd verify that the duplexers are properly tuned and the transmitter is clean before even starting down any other paths related to the channel 12 issue. IIRC, the Telewave cavities have adjustable coupling. If necessary, sacrifice a little extra loss for additional rejection if necessary. [Stu] I tuned the duplexer myself with a network analyzer and the transmitter looks clean. I have coupling set where I get about 1 dB through loss and the notches are at about 88 dB on TX and about 90 dB on RX. I also assume you're using all known-good interconnect cables (no foil+braid or other cables not suitable for duplex operation). [Stu] All cables are either Heliax or double braided. Are you using a Polyphaser or other type of surge arrestor? If so, try bypassing it. I've seen gas discharge tube type surge arrestors become noisemakers after absorbing a strike. [Stu] Yes but there is no difference in desense when it is removed. Has the VSWR changed at all on your antenna? If so, it could indicate water in a connector or the harness which will cause all kinds of grief, including wideband noise. [Stu] The problem has existed since the repeater was installed. It exists whether we duplex on a DB264 at 80 feet or a G7-220 at 15 feet, both fed with Heliax Finally, does the desense change appreciably if you vary transmitter power output (it probably will). Do you any have desense when running on just exciter power? [Stu] The desense is roughly proportional to transmit power. Barely perceptable at 20W (exciter only) with split antennas. A little worse at 20W (exciter only) using one antenna. Have tried both tube-type and solid state amplifiers at various power levels. --- Jeff WN3A
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
Stu, It looks to me as if you have covered almost all of the bases, and have eliminated every one of the typical causes of desense. However, there is one possibility that has not been mentioned: Leakage inside the Micor radio. Even with a careful duplex conversion, there are several sneak paths for extraneous signals to enter the Micor receiver. One ingress point is the tiny slots around the RCA plug at the input to the helical resonator block. A wrap of metal tape around that plug will seal the plug. Additional bypass capacitors and ferrite beads on DC supply leads may help. Try using a separate DC power supply for the receiver. Moreover, I suspect that the receiver needs more shielding. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Stu Benner Sent: Friday, January 25, 2008 1:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater Thanks to everyone for the replies so far. Please see comments embedded below. I think that they address most of the comments, questions, and recommendations posed by all to this point. If you suspect IMD between the channel 12 DTV transmitter and your Tx carrier, work on attenuating the DTV signal. Using cavity notch filters to reject the entire 6 MHz of DTV isn't too practical, so instead, try adding pass cavities on your Tx before the duplexer input. That will help determine if the IM is originating in your PA. An isolator *may* help, but with channel 12 being the better part of 20 MHz away (about 10%), it may not afford full protection -- isolators don't have infinite bandwidth. Likewise, finding a 250 watt 220 MHz isolator may not be easy. I think I have some 220 isolators that came off a combiner (Sinclair), but doubt they're good for 250 watts judging by their size. [Stu] Agree, notches don't work well for that plus we don't have handy any cavities that will tune there. Have used up to two BP cavities in the TX path along with a 2-stage isolator. No difference in desense is observed. If you suspect a rusty bolt mix, use an alternate antenna for testing. If nothing else, try a quarter-wave whip (suitable for operation at your 250 watts TPO), even if it's just temporarily mounted on the tower (be sure it's at a sufficient height to prevent desense due to close proximity to the repeater itself). [Stu] We're presently on split antennas. One is at about 80 ft., the other is at about 15 ft. This improves the desense on the order of 6 dB. Another good possibility is IM in your receiver front end (or preamp, if you're using one). Again, pass cavities are your friend here. Attenuate the channel 12 signal as much as possible and see if it makes a difference. Have you looked at what sigs are reaching your receiver input on a spectrum analyzer? With 15 dB of desense, you should be able to see the culprit(s); it's not like they're going to be buried in the noise if it's causing 15 dB of desense. [Stu] The desense is significant with or without a preamp. Worse with but I can't find my notes to quote numbers. Used up to 2 BP cavities on RX with no perceptible difference in desense. Have also installed a DCI 4-pole filter on RX and TX with no effect. Have looked at the receiver input with a spectrum analyzer. The most significant signal is the one FM broadcast transmitter at the site. Running power down on it or turning it off has no effect on the desense. Our TX signal at our RX input is consistent with our measured duplexer isolation (about -88 dBc or -34 dBm). Within several hundred kHz of the RX frequency there are no detectable narrowband signals. Even that 1 dB of desense would give me some agita. I'd verify that the duplexers are properly tuned and the transmitter is clean before even starting down any other paths related to the channel 12 issue. IIRC, the Telewave cavities have adjustable coupling. If necessary, sacrifice a little extra loss for additional rejection if necessary. [Stu] I tuned the duplexer myself with a network analyzer and the transmitter looks clean. I have coupling set where I get about 1 dB through loss and the notches are at about 88 dB on TX and about 90 dB on RX. I also assume you're using all known-good interconnect cables (no foil+braid or other cables not suitable for duplex operation). [Stu] All cables are either Heliax or double braided. Are you using a Polyphaser or other type of surge arrestor? If so, try bypassing it. I've seen gas discharge tube type surge arrestors become noisemakers after absorbing a strike. [Stu] Yes
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
--- Eric Lemmon [EMAIL PROTECTED] wrote: Stu, I think 250 watts is far too much power for that duplexer to properly isolate. Try running just your exciter, or try no more than 30 watts or so. My 220 repeater runs just 18 watts, and it is almost perfectly balanced. I am using the same Telewave duplexer, and I have zero desense. According to my CommShop program, you need more than 90 dB of isolation for 250 watts TX and 0.25 uV RX- and that's assuming a tube amplifier. The Telewave TPRD-2254 duplexer is spec'd at 85 dB, so it is borderline, even when perfectly tuned. You might try a sharply-tuned bandpass cavity to clean up the transmitter output, to see if sideband noise is causing the desense. Also, try a bandpass cavity on the RX input. As has been explained many times on this list, a BpBr duplexer has practically no bandpass effect, and what little effect there is, is very broad. 73, Eric Lemmon WB6FLY That was my thoughts also. Seems too much power for the ammount of isolation. Especially if a preamp is used on the receiver. I would like to know the modifications to the amplifier to get it to run that much power in repeater operation. I have one that will run around 500 watts but use it for ssb. As this was origionaly a 50 watt AM amp, I might see it running 100 to maybe 150 watts out in FM repeater service. Inside the amp are several pieces of coax. Is this double shielded or has it been changed to double shielding ? Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
Stu, I think 250 watts is far too much power for that duplexer to properly isolate. Try running just your exciter, or try no more than 30 watts or so. My 220 repeater runs just 18 watts, and it is almost perfectly balanced. I am using the same Telewave duplexer, and I have zero desense. According to my CommShop program, you need more than 90 dB of isolation for 250 watts TX and 0.25 uV RX- and that's assuming a tube amplifier. The Telewave TPRD-2254 duplexer is spec'd at 85 dB, so it is borderline, even when perfectly tuned. You might try a sharply-tuned bandpass cavity to clean up the transmitter output, to see if sideband noise is causing the desense. Also, try a bandpass cavity on the RX input. As has been explained many times on this list, a BpBr duplexer has practically no bandpass effect, and what little effect there is, is very broad. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Stu Benner Sent: Friday, January 25, 2008 9:52 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense Problem on 222 MHz Repeater Our group has substantial technical knowledge and experience, but we've been just about beaten down by a problem with our repeater. A brief overview of our situation follows. We have a 222 MHz repeater comprised of a converted Micor mobile, Telewave TPRD-2254 BpBr duplexer, AM-6155 PA modified for class C operation at 250W, and a DB-264JJ antenna at 80 ft. fed by 1/2' Heliax on a commercial FM broadcast tower . With the duplexer terminated into a load, we have about 1 dB degradation in sensitivity when transmitting. However, with the antenna connected to the duplexer, we experience in excess 15 dB of desensitization. We have eliminated other narrowband transmitters and analog TV transmitters as contributing factors. We are left with a channel 12 digital TV transmitter at an adjacent site as a key contributor to the problem. Our hypothesis is that we have broadband IMD products from the mix of our transmitter and the DTV transmitter that are appearing in and near our receiver passband. Is it a rusty bolt problem or is there some other non-linear component somewhere on the site or in our system that is the mixing point - we don't know. I'd be interested in beginning a dialog with anyone who might be able to give us some further insight into this problem. Regards, Stu Benner W3STU Boonsboro, MD
Re: [Repeater-Builder] Desense Problem on 222 MHz Repeater
Couple of thoughts from one who is not to technically oriented. 1. Have you tried putting any notch filters between the duplexer and rcvr. to notch the TX freq. ? 2. Have you checked all of your cables and heliax connecters for proper installation ? I only ask this because I was having erratic performance and desense on a 440 rptr. and found some bad duplexer cable connector installations when I started wiggling and moving them around. Another time while checking Fwd/Ref. power and SWR on o 160' peice of 1/2 heliax that I thought was good (and getting satisfactory readings on my Bird mtr.), I pulled the connectors of each end to inspect them. I found one connector had been improperly installed, the heliax shield had been twisted inside the connector to the point where it was almost touching the center conductor. Even though there was no direct contact between shield and the center conductor the RF on xmit. was desensing the rcvr. when the xmtr. keyed up. Reinstalling the bad cables and connectors solve the desense problem for me. -- Doug N3DAB/WPRX486/WPJL709 Stu Benner [EMAIL PROTECTED] wrote: = Our group has substantial technical knowledge and experience, but we've been just about beaten down by a problem with our repeater. A brief overview of our situation follows. We have a 222 MHz repeater comprised of a converted Micor mobile, Telewave TPRD-2254 BpBr duplexer, AM-6155 PA modified for class C operation at 250W, and a DB-264JJ antenna at 80 ft. fed by 1/2' Heliax on a commercial FM broadcast tower . With the duplexer terminated into a load, we have about 1 dB degradation in sensitivity when transmitting. However, with the antenna connected to the duplexer, we experience in excess 15 dB of desensitization. We have eliminated other narrowband transmitters and analog TV transmitters as contributing factors. We are left with a channel 12 digital TV transmitter at an adjacent site as a key contributor to the problem. Our hypothesis is that we have broadband IMD products from the mix of our transmitter and the DTV transmitter that are appearing in and near our receiver passband. Is it a rusty bolt problem or is there some other non-linear component somewhere on the site or in our system that is the mixing point - we don't know. I'd be interested in beginning a dialog with anyone who might be able to give us some further insight into this problem. Regards, Stu Benner W3STU Boonsboro, MD
Re: [Repeater-Builder] Desense Problem on 222 MHz Repeater
Hey Jeff: I think there are some out there that might question agita. Haven't heard that term in a while (and don't want to have it). Ciao, Tony Jeff DePolo wrote: We have a 222 MHz repeater comprised of a converted Micor mobile, Telewave TPRD-2254 BpBr duplexer, AM-6155 PA modified for class C operation at 250W, and a DB-264JJ antenna at 80 ft. fed by 1/2' Heliax on a commercial FM broadcast tower . With the duplexer terminated into a load, we have about 1 dB degradation in sensitivity when transmitting. However, with the antenna connected to the duplexer, we experience in excess 15 dB of desensitization. We have eliminated other narrowband transmitters and analog TV transmitters as contributing factors. We are left with a channel 12 digital TV transmitter at an adjacent site as a key contributor to the problem. Our hypothesis is that we have broadband IMD products from the mix of our transmitter and the DTV transmitter that are appearing in and near our receiver passband. Is it a rusty bolt problem or is there some other non-linear component somewhere on the site or in our system that is the mixing point - we don't know. If you suspect IMD between the channel 12 DTV transmitter and your Tx carrier, work on attenuating the DTV signal. Using cavity notch filters to reject the entire 6 MHz of DTV isn't too practical, so instead, try adding pass cavities on your Tx before the duplexer input. That will help determine if the IM is originating in your PA. An isolator *may* help, but with channel 12 being the better part of 20 MHz away (about 10%), it may not afford full protection -- isolators don't have infinite bandwidth. Likewise, finding a 250 watt 220 MHz isolator may not be easy. I think I have some 220 isolators that came off a combiner (Sinclair), but doubt they're good for 250 watts judging by their size. If you suspect a rusty bolt mix, use an alternate antenna for testing. If nothing else, try a quarter-wave whip (suitable for operation at your 250 watts TPO), even if it's just temporarily mounted on the tower (be sure it's at a sufficient height to prevent desense due to close proximity to the repeater itself). Another good possibility is IM in your receiver front end (or preamp, if you're using one). Again, pass cavities are your friend here. Attenuate the channel 12 signal as much as possible and see if it makes a difference. Have you looked at what sigs are reaching your receiver input on a spectrum analyzer? With 15 dB of desense, you should be able to see the culprit(s); it's not like they're going to be buried in the noise if it's causing 15 dB of desense. Even that 1 dB of desense would give me some agita. I'd verify that the duplexers are properly tuned and the transmitter is clean before even starting down any other paths related to the channel 12 issue. IIRC, the Telewave cavities have adjustable coupling. If necessary, sacrifice a little extra loss for additional rejection if necessary. I also assume you're using all known-good interconnect cables (no foil+braid or other cables not suitable for duplex operation). Are you using a Polyphaser or other type of surge arrestor? If so, try bypassing it. I've seen gas discharge tube type surge arrestors become noisemakers after absorbing a strike. Has the VSWR changed at all on your antenna? If so, it could indicate water in a connector or the harness which will cause all kinds of grief, including wideband noise. Finally, does the desense change appreciably if you vary transmitter power output (it probably will). Do you any have desense when running on just exciter power? --- Jeff WN3A Yahoo! Groups Links
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
We have a 222 MHz repeater comprised of a converted Micor mobile, Telewave TPRD-2254 BpBr duplexer, AM-6155 PA modified for class C operation at 250W, and a DB-264JJ antenna at 80 ft. fed by 1/2' Heliax on a commercial FM broadcast tower . With the duplexer terminated into a load, we have about 1 dB degradation in sensitivity when transmitting. However, with the antenna connected to the duplexer, we experience in excess 15 dB of desensitization. We have eliminated other narrowband transmitters and analog TV transmitters as contributing factors. We are left with a channel 12 digital TV transmitter at an adjacent site as a key contributor to the problem. Our hypothesis is that we have broadband IMD products from the mix of our transmitter and the DTV transmitter that are appearing in and near our receiver passband. Is it a rusty bolt problem or is there some other non-linear component somewhere on the site or in our system that is the mixing point - we don't know. If you suspect IMD between the channel 12 DTV transmitter and your Tx carrier, work on attenuating the DTV signal. Using cavity notch filters to reject the entire 6 MHz of DTV isn't too practical, so instead, try adding pass cavities on your Tx before the duplexer input. That will help determine if the IM is originating in your PA. An isolator *may* help, but with channel 12 being the better part of 20 MHz away (about 10%), it may not afford full protection -- isolators don't have infinite bandwidth. Likewise, finding a 250 watt 220 MHz isolator may not be easy. I think I have some 220 isolators that came off a combiner (Sinclair), but doubt they're good for 250 watts judging by their size. If you suspect a rusty bolt mix, use an alternate antenna for testing. If nothing else, try a quarter-wave whip (suitable for operation at your 250 watts TPO), even if it's just temporarily mounted on the tower (be sure it's at a sufficient height to prevent desense due to close proximity to the repeater itself). Another good possibility is IM in your receiver front end (or preamp, if you're using one). Again, pass cavities are your friend here. Attenuate the channel 12 signal as much as possible and see if it makes a difference. Have you looked at what sigs are reaching your receiver input on a spectrum analyzer? With 15 dB of desense, you should be able to see the culprit(s); it's not like they're going to be buried in the noise if it's causing 15 dB of desense. Even that 1 dB of desense would give me some agita. I'd verify that the duplexers are properly tuned and the transmitter is clean before even starting down any other paths related to the channel 12 issue. IIRC, the Telewave cavities have adjustable coupling. If necessary, sacrifice a little extra loss for additional rejection if necessary. I also assume you're using all known-good interconnect cables (no foil+braid or other cables not suitable for duplex operation). Are you using a Polyphaser or other type of surge arrestor? If so, try bypassing it. I've seen gas discharge tube type surge arrestors become noisemakers after absorbing a strike. Has the VSWR changed at all on your antenna? If so, it could indicate water in a connector or the harness which will cause all kinds of grief, including wideband noise. Finally, does the desense change appreciably if you vary transmitter power output (it probably will). Do you any have desense when running on just exciter power? --- Jeff WN3A
RE: [Repeater-Builder] Desense Problem on 222 MHz Repeater
Thanks to everyone for the replies so far. Please see comments embedded below. I think that they address most of the comments, questions, and recommendations posed by all to this point. If you suspect IMD between the channel 12 DTV transmitter and your Tx carrier, work on attenuating the DTV signal. Using cavity notch filters to reject the entire 6 MHz of DTV isn't too practical, so instead, try adding pass cavities on your Tx before the duplexer input. That will help determine if the IM is originating in your PA. An isolator *may* help, but with channel 12 being the better part of 20 MHz away (about 10%), it may not afford full protection -- isolators don't have infinite bandwidth. Likewise, finding a 250 watt 220 MHz isolator may not be easy. I think I have some 220 isolators that came off a combiner (Sinclair), but doubt they're good for 250 watts judging by their size. [Stu] Agree, notches don't work well for that plus we don't have handy any cavities that will tune there. Have used up to two BP cavities in the TX path along with a 2-stage isolator. No difference in desense is observed. If you suspect a rusty bolt mix, use an alternate antenna for testing. If nothing else, try a quarter-wave whip (suitable for operation at your 250 watts TPO), even if it's just temporarily mounted on the tower (be sure it's at a sufficient height to prevent desense due to close proximity to the repeater itself). [Stu] We're presently on split antennas. One is at about 80 ft., the other is at about 15 ft. This improves the desense on the order of 6 dB. Another good possibility is IM in your receiver front end (or preamp, if you're using one). Again, pass cavities are your friend here. Attenuate the channel 12 signal as much as possible and see if it makes a difference. Have you looked at what sigs are reaching your receiver input on a spectrum analyzer? With 15 dB of desense, you should be able to see the culprit(s); it's not like they're going to be buried in the noise if it's causing 15 dB of desense. [Stu] The desense is significant with or without a preamp. Worse with but I can't find my notes to quote numbers. Used up to 2 BP cavities on RX with no perceptable difference in desense. Have also installed a DCI 4-pole filter on RX and TX with no effect. Have looked at the receiver input with a spectrum analyzer. The most significant signal is the one FM broadcast transmitter at the site. Running power down on it or turning it off has no effect on the desense. Our TX signal at our RX input is consistent with our measured duplexer isolation (about -88 dBc or -34 dBm). Within several hundred kHz of the RX frequency there are no detectable narrowband signals. Even that 1 dB of desense would give me some agita. I'd verify that the duplexers are properly tuned and the transmitter is clean before even starting down any other paths related to the channel 12 issue. IIRC, the Telewave cavities have adjustable coupling. If necessary, sacrifice a little extra loss for additional rejection if necessary. [Stu] I tuned the duplexer myself with a network analyzer and the transmitter looks clean. I have coupling set where I get about 1 dB through loss and the notches are at about 88 dB on TX and about 90 dB on RX. I also assume you're using all known-good interconnect cables (no foil+braid or other cables not suitable for duplex operation). [Stu] All cables are either Heliax or double braided. Are you using a Polyphaser or other type of surge arrestor? If so, try bypassing it. I've seen gas discharge tube type surge arrestors become noisemakers after absorbing a strike. [Stu] Yes but there is no difference in desense when it is removed. Has the VSWR changed at all on your antenna? If so, it could indicate water in a connector or the harness which will cause all kinds of grief, including wideband noise. [Stu] The problem has existed since the repeater was installed. It exists whether we duplex on a DB264 at 80 feet or a G7-220 at 15 feet, both fed with Heliax Finally, does the desense change appreciably if you vary transmitter power output (it probably will). Do you any have desense when running on just exciter power? [Stu] The desense is roughly proportional to transmit power. Barely perceptable at 20W (exciter only) with split antennas. A little worse at 20W (exciter only) using one antenna. Have tried both tube-type and solid state amplifiers at various power levels. --- Jeff WN3A
Re: [Repeater-Builder] Desense Problem on 222 MHz Repeater
Any chance you can connect a spectrum analyzer to the duplexers receieve port? Make tests to look at the IF range and the receiver range with and without the transmitter active. This will tell you alot. For example on a 2m repeater we had a dirty SMPS in the vicinity of the antenna that opperated at approx. 600kHz. As soon as the transmitter came on at any level 2 sidebands were created + and - 600kHz from the transmitters carrier.
Re: [Repeater-Builder] Desense
[EMAIL PROTECTED] wrote: Well the local ham fest rolled into town last weekend and I was able to get some cans. One of which is a DB products bp can model sp6610C. A friend tuned it up for me and I put it between the MASTRII on the receive side and the receive side of the db4048 duplexer that I have which wasn't providing proper isolation. It's like I have a new repeater. I have not been able to do any extended testing yet but I can run lower power on my mobile around town then before and people on HTs that couldn't hit the machine from in their house can now do so full quieting. Now if you want to take the next step, and go from a thinking man to a knowing man... Use an Iso-T or directional coupler, and a signal generator on your input frequency and some way to measure the 12dB SINAD point of the receiver. (If you're using a service monitor, they'll usually do both the signal generation at an accurate power level, and the SINAD measurement, but you can also use a much cheaper standalone signal generator and something like a Sinadder S/N measurement device.) Measure the real-world receiver sensitivity numbers, put them in the engineering logbook, and track it over time. It allows for a lot of things, like knowing if your receiver suddenly has gone deaf, etc. Also allows you to track it over time to see if you have a slow degradation going on, site noise going up, etc. While you're set up to do that test, desense is easy to test for, too. Inject a weak signal into the receiver and set it to the noisy 12 dB SINAD point, with the repeater transmitter off. Turn transmitter on. If weak signal disappears or gets noisy, you don't have enough isolation, you have leaky interconnect cables, or something else is wrong... you have desense. A properly working system should have none. None at all. You should hear no difference at all with the transmitter on or off. If you have desense, leave the transmitter on, and turn the signal generator up until you're back to 12 dB SINAD. Now you know how much the power level had to change to get back to your arbitrary reference point, and therefore, you know how many dB of desense your system is experiencing, so you have hard numbers as to how bad the desense is. Then you can share here on the list, and folks that have used the type of radio and setup you've built -- can tell you if that's what they would expect to see from your specific radio type, etc. If you get in the habit of doing these tests at least once a year on established systems, and/or during an installation of a new system, and recording all the numbers -- you then know right away that the system isn't performing as well as it should, opposed to finding out by shotgunning in more filtering later on. Knowing up-front is nicer, once you get in the habit of going through the extra (minor) work of doing the real tests. Nate WY0X
Re: [Repeater-Builder] Desense
If I could afford that equipment I would do that. However the thought of spending as much on test equipment as a new car is a little tough. We do have a service monitor in the group I hang out with but it does not have a tracking generator. Vern On Tue, 16 Oct 2007 11:15:11 -0600 Nate Duehr [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote: Well the local ham fest rolled into town last weekend and I was able to get some cans. One of which is a DB products bp can model sp6610C. A friend tuned it up for me and I put it between the MASTRII on the receive side and the receive side of the db4048 duplexer that I have which wasn't providing proper isolation. It's like I have a new repeater. I have not been able to do any extended testing yet but I can run lower power on my mobile around town then before and people on HTs that couldn't hit the machine from in their house can now do so full quieting. Now if you want to take the next step, and go from a thinking man to a knowing man... Use an Iso-T or directional coupler, and a signal generator on your input frequency and some way to measure the 12dB SINAD point of the receiver. (If you're using a service monitor, they'll usually do both the signal generation at an accurate power level, and the SINAD measurement, but you can also use a much cheaper standalone signal generator and something like a Sinadder S/N measurement device.) Measure the real-world receiver sensitivity numbers, put them in the engineering logbook, and track it over time. It allows for a lot of things, like knowing if your receiver suddenly has gone deaf, etc. Also allows you to track it over time to see if you have a slow degradation going on, site noise going up, etc. While you're set up to do that test, desense is easy to test for, too. Inject a weak signal into the receiver and set it to the noisy 12 dB SINAD point, with the repeater transmitter off. Turn transmitter on. If weak signal disappears or gets noisy, you don't have enough isolation, you have leaky interconnect cables, or something else is wrong... you have desense. A properly working system should have none. None at all. You should hear no difference at all with the transmitter on or off. If you have desense, leave the transmitter on, and turn the signal generator up until you're back to 12 dB SINAD. Now you know how much the power level had to change to get back to your arbitrary reference point, and therefore, you know how many dB of desense your system is experiencing, so you have hard numbers as to how bad the desense is. Then you can share here on the list, and folks that have used the type of radio and setup you've built -- can tell you if that's what they would expect to see from your specific radio type, etc. If you get in the habit of doing these tests at least once a year on established systems, and/or during an installation of a new system, and recording all the numbers -- you then know right away that the system isn't performing as well as it should, opposed to finding out by shotgunning in more filtering later on. Knowing up-front is nicer, once you get in the habit of going through the extra (minor) work of doing the real tests. Nate WY0X
Re: [Repeater-Builder] Desense
[EMAIL PROTECTED] wrote: If I could afford that equipment I would do that. However the thought of spending as much on test equipment as a new car is a little tough. Totally understand. Although many good service monitors can be had for the price of a USED car, not a new one -- if that's helpful information. :-) (I hunted for three years and found an IFR 1500 for $2K in great condition, with a fairly recent calibration sticker.) We do have a service monitor in the group I hang out with but it does not have a tracking generator. A tracking generator is not necessary (or desired) for this test. Those are used for tuning duplexers, and sweeping antennas -- etc. Things that require a sweep of frequency. You don't need to sweep the receiver - you just need a variable strength signal on the receiver input for desense and receiver sensitivity tests. A service monitor is a signal generator by definition, so you have just about everything you need to do the tests already. Depending on what type it is, it may also be able to measure SINAD for you. If not, with a little practice you can learn to hear about where 12 dB SINAD is, and how it relates by ear to a full-quieting signal. Not as accurate at all, but you could get a ballpark idea of how well your receiver is working. The desense test only requires a known 12 dB SINAD measurement if you're trying to measure how MUCH desense is present. Any weak signal as long as it's consistent (even a friend with an HT on a fixed antenna far away or through a lot of attenuation and very low power) can be used as a weak signal source to check whether desense is present. What model/brand of service monitor is it? Perhaps we can help explain how to set the test up. I've played with a Cushman CE-5, a Motorola 2600 (?) a couple of older Motorolas, IFR 1200's and 1500's and HP 8920 series. I'm sure others here could explain how to set up other service monitors... Nate WY0X
Re: [Repeater-Builder] Desense
Trying to make a 30 year old Motrac a reliable repeater shows one doesn't have desense G-d gave him Ken (famous quotes 101)
Re: [Repeater-Builder] Desense
I think it's an HP of some sort but someone is using it right now and we have to get it back. The person who owns it actually has 2 of them but one needs some work and he is probably going to sell it rather than fix it. On Tue, 16 Oct 2007 12:09:09 -0600 Nate Duehr [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote: If I could afford that equipment I would do that. However the thought of spending as much on test equipment as a new car is a little tough. Totally understand. Although many good service monitors can be had for the price of a USED car, not a new one -- if that's helpful information. :-) (I hunted for three years and found an IFR 1500 for $2K in great condition, with a fairly recent calibration sticker.) We do have a service monitor in the group I hang out with but it does not have a tracking generator. A tracking generator is not necessary (or desired) for this test. Those are used for tuning duplexers, and sweeping antennas -- etc. Things that require a sweep of frequency. You don't need to sweep the receiver - you just need a variable strength signal on the receiver input for desense and receiver sensitivity tests. A service monitor is a signal generator by definition, so you have just about everything you need to do the tests already. Depending on what type it is, it may also be able to measure SINAD for you. If not, with a little practice you can learn to hear about where 12 dB SINAD is, and how it relates by ear to a full-quieting signal. Not as accurate at all, but you could get a ballpark idea of how well your receiver is working. The desense test only requires a known 12 dB SINAD measurement if you're trying to measure how MUCH desense is present. Any weak signal as long as it's consistent (even a friend with an HT on a fixed antenna far away or through a lot of attenuation and very low power) can be used as a weak signal source to check whether desense is present. What model/brand of service monitor is it? Perhaps we can help explain how to set the test up. I've played with a Cushman CE-5, a Motorola 2600 (?) a couple of older Motorolas, IFR 1200's and 1500's and HP 8920 series. I'm sure others here could explain how to set up other service monitors... Nate WY0X
Re: [Repeater-Builder] Desense
[EMAIL PROTECTED] wrote: I think it's an HP of some sort but someone is using it right now and we have to get it back. The person who owns it actually has 2 of them but one needs some work and he is probably going to sell it rather than fix it. If it's an HP 8920 series, that's virtually top of the line for analog repeater work, and it would be very wise of you to both get it back (!) so it doesn't wander off, and also to learn how to use it. They're worth a bunch of $. There's virtually nothing you can't fix and/or measure/see with one of those... especially if they have the Spectrum Analyzer/Tracking Generator option installed, which you said it doesn't have. But even without it, if it's an 8920 series, that's an excellent piece of test gear. If it is one of the later model HP's, you shouldn't waste any time in learning its features and how to use it! Be cautious, some models (ones with the option for high accuracy) have power input limitations, and you can damage them if you put too much power into them. They're usually labeled clearly with the power limitation near the input N-connector. Get it in-hand, get the model number off of it, and ask here on the list for assistance... a number of folks here can help with how to set up basic tests on your repeater with that test gear, if it's what I think it is. I'm not going to guess, though. Guessing leads to assumptions and that leads to ... well we all know what the word assume stands for -- but it also leads to poor repeater performance. (GRIN) The number one advice I got from veteran repeater-builders when I started working on these things... don't guess. Be scientific. Measure everything, measure again, then compare the measurements against the manufacturer's specifications for the radio. If they don't match, come up with a theory and then make incremental changes to alleviate the problem(s) one at a time, re-measuring along the way. A scientific versus an amateur approach, if you will. It'll pay big dividends in your repeater's performance, and also in maintenance time spent hunting problems down. It's a lot easier to KNOW what's not performing to spec versus guessing or hunches. The basics are: - Everything on-frequency (receiver and transmitter/exciter), and deviation levels set accurately? (Your service monitor can help here, as long as it's accurate... good to make sure when starting with an unknown service monitor, and to always check its receiver against a known source before starting on-site checks.) - Whether or not the system exhibits any desense (easiest test of all... already documented in previous posting) - Receiver sensitivity without antenna system connected. (Known power level signal generator/RF signal source needed here and preferrably a way to measure the 12dB SINAD point.) - *Usable* receiver sensitivity with antenna system connected (Iso-T or directional coupler additionally needed, and a way to measure the 12 dB SINAD point of the receiver.) ^^^ All of the above affected by whether or not you have a pre-amp installed, the quality of your interconnect cables, and transmitter power versus isolation offered by your duplexer. Other things which can factor in: - Transmitter cleanliness -- is it clean or is it throwing crud up and down the band. (A great way to become an unwelcome neighbor to all, very quickly.) - Antenna performance (does it duplex well?) - Feedline quality (forward loss, return loss -- how much RF can get through that cable?) - Site noise or other high-power transmitters (even transmitters off-frequency outside the ham bands can overload the front end of low-quality receivers if they're really powerful on a nearby antenna!) Etc etc etc... it's really good to measure everything before starting and then, as I mentioned, make incremental changes and see what helps and knowing exactly how much. Your repeater users will love it if you can squeak the maximum performance out of your systems. Although, there's always going to be that guy who wants to hit the repeater using 150 mW from his basement 20 or more miles away... some people just don't realize when they're asking you to push the laws of physics and the typical performance of radio gear right to the limits! (GRIN) Nate WY0X
Re: [Repeater-Builder] Desense
Thanks. This is a great write up and one for the archives. As soon as we get over to pickup the service monitor (and some free tower sections) I will let you know the specs on it and we will start trying some of these tests. Vern KI4ONW On Tue, 16 Oct 2007 13:25:44 -0600 Nate Duehr [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote: I think it's an HP of some sort but someone is using it right now and we have to get it back. The person who owns it actually has 2 of them but one needs some work and he is probably going to sell it rather than fix it. If it's an HP 8920 series, that's virtually top of the line for analog repeater work, and it would be very wise of you to both get it back (!) so it doesn't wander off, and also to learn how to use it. They're worth a bunch of $. There's virtually nothing you can't fix and/or measure/see with one of those... especially if they have the Spectrum Analyzer/Tracking Generator option installed, which you said it doesn't have. But even without it, if it's an 8920 series, that's an excellent piece of test gear. If it is one of the later model HP's, you shouldn't waste any time in learning its features and how to use it! Be cautious, some models (ones with the option for high accuracy) have power input limitations, and you can damage them if you put too much power into them. They're usually labeled clearly with the power limitation near the input N-connector. Get it in-hand, get the model number off of it, and ask here on the list for assistance... a number of folks here can help with how to set up basic tests on your repeater with that test gear, if it's what I think it is. I'm not going to guess, though. Guessing leads to assumptions and that leads to ... well we all know what the word assume stands for -- but it also leads to poor repeater performance. (GRIN) The number one advice I got from veteran repeater-builders when I started working on these things... don't guess. Be scientific. Measure everything, measure again, then compare the measurements against the manufacturer's specifications for the radio. If they don't match, come up with a theory and then make incremental changes to alleviate the problem(s) one at a time, re-measuring along the way. A scientific versus an amateur approach, if you will. It'll pay big dividends in your repeater's performance, and also in maintenance time spent hunting problems down. It's a lot easier to KNOW what's not performing to spec versus guessing or hunches. The basics are: - Everything on-frequency (receiver and transmitter/exciter), and deviation levels set accurately? (Your service monitor can help here, as long as it's accurate... good to make sure when starting with an unknown service monitor, and to always check its receiver against a known source before starting on-site checks.) - Whether or not the system exhibits any desense (easiest test of all... already documented in previous posting) - Receiver sensitivity without antenna system connected. (Known power level signal generator/RF signal source needed here and preferrably a way to measure the 12dB SINAD point.) - *Usable* receiver sensitivity with antenna system connected (Iso-T or directional coupler additionally needed, and a way to measure the 12 dB SINAD point of the receiver.) ^^^ All of the above affected by whether or not you have a pre-amp installed, the quality of your interconnect cables, and transmitter power versus isolation offered by your duplexer. Other things which can factor in: - Transmitter cleanliness -- is it clean or is it throwing crud up and down the band. (A great way to become an unwelcome neighbor to all, very quickly.) - Antenna performance (does it duplex well?) - Feedline quality (forward loss, return loss -- how much RF can get through that cable?) - Site noise or other high-power transmitters (even transmitters off-frequency outside the ham bands can overload the front end of low-quality receivers if they're really powerful on a nearby antenna!) Etc etc etc... it's really good to measure everything before starting and then, as I mentioned, make incremental changes and see what helps and knowing exactly how much. Your repeater users will love it if you can squeak the maximum performance out of your systems. Although, there's always going to be that guy who wants to hit the repeater using 150 mW from his basement 20 or more miles away... some people just don't realize when they're asking you to push the laws of physics and the typical performance of radio gear right to the limits! (GRIN) Nate WY0X
Re: [Repeater-Builder] Desense
On 2/26/07, Jeff Kashinsky [EMAIL PROTECTED] wrote: I am building a 440 portable repeater out of a pair of GM300 radios and a Harris Alpha mobile duplexer. I believe that I tuned the duplexer properly and it notches the xmit signal by about 55db on the receive side. Using my signal generator as a source, it takes about 10db more signal to key the contoller with the transmitter on than with it off. I am wondering if this is normal or if I have more work to do. Depends on if you want it to work well or not. :-) I vote, more work. Are your measurements made when terminated into a good quality 50 ohm dummy load, or a real antenna system? Is there noise on your receive frequency (if hooked to an antenna)? Make sure you're using double-shielded good quality cables and connectors -- keep all that TX RF *in* the cables, and (hopefully) headed out the antenna. You don't want the TX cable leaking directly into the jumper from the receive side of the duplexer into the RX. (Kinda makes the duplexer worthless, ya know?) What power level is your TX set at? If you know you have 55dB of isolation, how much do you need to remove at the RX frequency? Is the TX clean? Do you have less desense if you turn the TX power down? What's the VSWR look like? Etc... Work from known things toward the unknown. You know (if you've tested it) at what level your receiver receives. You know how much power the TX is producing. You know if your antenna system is radiating all the power, or if some is getting reflected in the cabling. You next need to know what the TX does 5 MHz away, and whether or not 55dB of isolation is enough. Nate WY0X
Re: [Repeater-Builder] desense, blocking or capture?
skipp025 wrote: So would/should we actually call the below problem desense, blocking or capture of the repeater receiver? s. Years ago an upside down repeater in New Mexico on the intertie using PL access would regularly be de-sensed by one in Texas 300 miles away in the spring with the enhanced propagation. This one was finally cured when the Texas repeater used a PL to access. Rarely were both systems active at the same time. ps: or some other label..? Blocking-definitely. Desense of course implies a loss of sensitivity, which is not happening. Capture implies that the receiver still has it's squelch open, to me anyway. If it was CSQ, or the same tone, that would apply. IMHO... Blocking is used in the commercial world (especially cellular) to indicate that something external to the radio system is preventing the rx from hearing the desired signal, and causing it to mute. -- Jim Barbour WD8CHL
Re: [Repeater-Builder] Desense
At 10:34 AM 2/26/2007, you wrote: I am building a 440 portable repeater out of a pair of GM300 radios and a Harris Alpha mobile duplexer. I believe that I tuned the duplexer properly and it notches the xmit signal by about 55db on the receive side. Using my signal generator as a source, it takes about 10db more signal to key the contoller with the transmitter on than with it off. I am wondering if this is normal or if I have more work to do. ---You didn't say what the model of the duplexer is and it is hard to say if you're meeting spec or not without that info. How many cavities? How long are the cavities? Also, when you tuned the duplexer did you make sure you have a known 50 ohm on EACH PORT (which usually involves using 3 or 6 dB pads)? Also how did you tune it? More info would be good in order to help! Ken -- President and CTO - Arcom Communications Makers of the world famous RC210 Repeater Controller and accessories. http://www.arcomcontrollers.com/ Authorized Dealers for Kenwood and Telewave and we offer complete repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net
Re: [Repeater-Builder] Desense im guessing/Preamp-n-Pads
I use small 2 watt attenuators with male BNC on one end and female on the other. There are various manufacturers and I see them often at hamfests. You'll find them anywhere from $0.25 to $10.00 each. Shop wisely and test the ones you get to make sure they haven't been smoked. I use two of these 3 db pads on my little Bird Termiline 250 milliwatt wattmeter which is a great tool for testing Mastr II exciters. 73, Tony W4ZT Brent wrote: Thats what im looking for Better signal to noise ratio ! Right now it is amplifing more than what is needed. I will experiment with this 8 and 10db pads i have. I am interested in what type of pad people are using, since this preamp is mounted inside the mastr II vhf receiver when i received it its location might need to be or should be moved.. but if i intend to leave it there it has a bnc to rca jumper installed from the preamp to the receiver, and i would need to install the pad there. Brent - Original Message - From: Tony King, W4ZT [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, March 24, 2005 11:22 PM Subject: Re: [Repeater-Builder] Desense im guessing? Cody Hayden wrote: db pads are bandaids and not cures..get a better duplexer..problem solved.. It is common practice to use 6 to 10 db of attenuation between a new high gain (typically as much as +18 db) GaAsFET low noise amplifier and an older receiver. The gain of the preamp is about 10 db higher than you need for the receiver yet you can gain benefits from the low noise front end and high intermod resistance. Placing the attenuator between the preamp and the receiver doesn't hurt the noise figure yet keeps the receiver front end input signal within acceptable limits. It doesn't reduce the usable sensitivity of the receiver either. The attenuator doesn't make up for deficiencies in a duplexer but it certainly can slam the door on other problems many of us have faced with excessive gain ahead of our older less sensitive receiver. The result is a much lower noise front end with moderately higher gain. Bottom line: better signal to noise ratio. --- Brent [EMAIL PROTECTED] wrote: One of my 2m repeater has a problem.snip 73, Tony W4ZT Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.8.1 - Release Date: 3/23/2005 Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
I had bad desense on a uhf msf 5000 with a cellwave 526 duplexer and aar preamp. Whenever I added the preamp I had bad desense. Went crazy adding filtering in the tx, rx and duplexer tuning. After days of playing around found I had a bad jumper cable between the repeater and ant that was generating noise. Replaced the cable and everything worked fine with no pad. Mark KB1IOZ --- Joe [EMAIL PROTECTED] wrote: Actually, try somewhere between .5 and 2dB BEFORE the preamp, you might be surprised that effective sensitivity will go UP an d desense will go DOWN. Joe Dave Baughn [EMAIL PROTECTED] wrote: = Try adding a 10 dB pad AFTER the preamp. Should not affect sensitivity but may help your desense. AAR preamp has more gain than necessary. Yahoo! Groups Links [EMAIL PROTECTED] __ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/ Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
At 3/24/2005 08:25 AM, you wrote: I had bad desense on a uhf msf 5000 with a cellwave 526 duplexer and aar preamp. Whenever I added the preamp I had bad desense. Went crazy adding filtering in the tx, rx and duplexer tuning. After days of playing around found I had a bad jumper cable between the repeater and ant that was generating noise. Replaced the cable and everything worked fine with no pad. Mark KB1IOZ Let me guess: the bad jumper was RG-8 or RG-213 was between the duplexer antenna? Bob NO6B Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
db pads are bandaids and not cures..get a better duplexer..problem solved.. --- Brent [EMAIL PROTECTED] wrote: One of my 2m repeater has a problem. It is a GE Mastr II base/repeater. have a set of wacom WP-639 on the machine, and a ARR preamp. ..a user 2 air miles fromt he site is wiped out of the receiver while the Tx is On, I turn the PA down below 20watts and he ( or all users) are clear. I have tried two different antennas before thinking about the duplexers, and want to double check other options before the cans.. these were factory tuned..cans. any thought or suggestions Thanks Brent -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links [EMAIL PROTECTED] __ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/ Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
Cody Hayden wrote: db pads are bandaids and not cures..get a better duplexer..problem solved.. It is common practice to use 6 to 10 db of attenuation between a new high gain (typically as much as +18 db) GaAsFET low noise amplifier and an older receiver. The gain of the preamp is about 10 db higher than you need for the receiver yet you can gain benefits from the low noise front end and high intermod resistance. Placing the attenuator between the preamp and the receiver doesn't hurt the noise figure yet keeps the receiver front end input signal within acceptable limits. It doesn't reduce the usable sensitivity of the receiver either. The attenuator doesn't make up for deficiencies in a duplexer but it certainly can slam the door on other problems many of us have faced with excessive gain ahead of our older less sensitive receiver. The result is a much lower noise front end with moderately higher gain. Bottom line: better signal to noise ratio. --- Brent [EMAIL PROTECTED] wrote: One of my 2m repeater has a problem.snip 73, Tony W4ZT Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing/Preamp-n-Pads
Thats what im looking for Better signal to noise ratio ! Right now it is amplifing more than what is needed. I will experiment with this 8 and 10db pads i have. I am interested in what type of pad people are using, since this preamp is mounted inside the mastr II vhf receiver when i received it its location might need to be or should be moved.. but if i intend to leave it there it has a bnc to rca jumper installed from the preamp to the receiver, and i would need to install the pad there. Brent - Original Message - From: Tony King, W4ZT [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, March 24, 2005 11:22 PM Subject: Re: [Repeater-Builder] Desense im guessing? Cody Hayden wrote: db pads are bandaids and not cures..get a better duplexer..problem solved.. It is common practice to use 6 to 10 db of attenuation between a new high gain (typically as much as +18 db) GaAsFET low noise amplifier and an older receiver. The gain of the preamp is about 10 db higher than you need for the receiver yet you can gain benefits from the low noise front end and high intermod resistance. Placing the attenuator between the preamp and the receiver doesn't hurt the noise figure yet keeps the receiver front end input signal within acceptable limits. It doesn't reduce the usable sensitivity of the receiver either. The attenuator doesn't make up for deficiencies in a duplexer but it certainly can slam the door on other problems many of us have faced with excessive gain ahead of our older less sensitive receiver. The result is a much lower noise front end with moderately higher gain. Bottom line: better signal to noise ratio. --- Brent [EMAIL PROTECTED] wrote: One of my 2m repeater has a problem.snip 73, Tony W4ZT Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.8.1 - Release Date: 3/23/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.8.1 - Release Date: 3/23/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
Actually, try somewhere between .5 and 2dB BEFORE the preamp, you might be surprised that effective sensitivity will go UP an d desense will go DOWN. Joe Dave Baughn [EMAIL PROTECTED] wrote: = Try adding a 10 dB pad AFTER the preamp. Should not affect sensitivity but may help your desense. AAR preamp has more gain than necessary. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense, I'm guessing?
Eric Lemmon wrote: For those who may not have the Wacom catalog handy, the WP-643 duplexer comprises six 8 cavities that are rated at 102 dB isolation at 600 kHz spacing, with 2.2 dB insertion loss. Four of the cavities are BpBr, and two are bandpass only. The WP-639 duplexer comprises four 5 BpBr cavities that are rated at 80 dB isolation at 600 kHz spacing, with 1.5 dB insertion loss. Needless to say, the WP-643 is vastly superior to the WP-639 at 2m spacing. You could use two of the WP-639 cavities for bandpass application, if you replaced the single BpBr coupling loop with two Bp loops on each cavity. Try the WP-643 in stock form first. I totally agree with Eric's suggestions. Kevin Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense, I'm guessing?
Kevin, Eric and all the WP-643's work great. And I dont even have the preamp installed and since i am happy with the performace with out the preamp and and the tx to rx range is about equal. It is locked Down and covers on. Thanks 6 8 cans are the way to go. - Original Message - From: Kevin Custer [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tuesday, March 22, 2005 5:26 AM Subject: Re: [Repeater-Builder] Desense, I'm guessing? Eric Lemmon wrote: For those who may not have the Wacom catalog handy, the WP-643 duplexer comprises six 8 cavities that are rated at 102 dB isolation at 600 kHz spacing, with 2.2 dB insertion loss. Four of the cavities are BpBr, and two are bandpass only. The WP-639 duplexer comprises four 5 BpBr cavities that are rated at 80 dB isolation at 600 kHz spacing, with 1.5 dB insertion loss. Needless to say, the WP-643 is vastly superior to the WP-639 at 2m spacing. You could use two of the WP-639 cavities for bandpass application, if you replaced the single BpBr coupling loop with two Bp loops on each cavity. Try the WP-643 in stock form first. I totally agree with Eric's suggestions. Kevin Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
Brent wrote: One of my 2m repeater has a problem. It is a GE Mastr II base/repeater. have a set of wacom WP-639 on the machine, and a ARR preamp. ..a user 2 air miles fromt he site is wiped out of the receiver while the Tx is On, I turn the PA down below 20watts and he ( or all users) are clear. I have tried two different antennas before thinking about the duplexers, and want to double check other options before the cans.. these were factory tuned..cans. any thought or suggestions Not enough duplexer. For a 50 to 100 watt Station with a receiver preamp you should have *at least* a WP-641, and that may not be enough unless its a PLL exciter type. Kevin Custer Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
Kevin Thanks I just look back at the meter and I stated 20Watts it was NOTit was 5 watts. with over 5 watts it causes the desense Problem.. I would think that since this is a PLL exciter and im am only needing 15-25 watts out that it should do ok .. what would your thoughts be about adding 2 10 pass cav. to the receiver side.. and or should i go with out the preamp. - Original Message - From: Kevin Custer [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, March 21, 2005 8:25 PM Subject: Re: [Repeater-Builder] Desense im guessing? Brent wrote: One of my 2m repeater has a problem. It is a GE Mastr II base/repeater. have a set of wacom WP-639 on the machine, and a ARR preamp. ..a user 2 air miles fromt he site is wiped out of the receiver while the Tx is On, I turn the PA down below 20watts and he ( or all users) are clear. I have tried two different antennas before thinking about the duplexers, and want to double check other options before the cans.. these were factory tuned..cans. any thought or suggestions Not enough duplexer. For a 50 to 100 watt Station with a receiver preamp you should have *at least* a WP-641, and that may not be enough unless its a PLL exciter type. Kevin Custer Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
Brent wrote: Kevin Thanks I just look back at the meter and I stated 20Watts it was NOT it was 5 watts. with over 5 watts it causes the desense Problem.. Cutting the power can be a double edged sword. While it reduces the shear power level, cutting the power down too far in Class C amplification can cause spurious emissions. The end result is cutting down the power many not be very beneficial, in fact, it *might* make matter worse. I would think that since this is a PLL exciter and im am only needing 15-25 watts out that it should do ok .. What is the power amplifier capable of? 110 watts? what would your thoughts be about adding 2 10 pass cav. to the receiver side.. and or should i go with out the preamp. First thing I'd do is bypass the preamp and see if you can get the thing to duplex. Then, start adding your bells and whistles. Kevin Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
On the duplexers the specs state I should have about 1.5 db loss on the TX port... I just measured the power output into a dummy load. from just the TX'er. it is set back to 30watts out.. I then hooked the duplexers back up and measured again. I have 12 watts into the same dummy load.. with little over 3db loss I am thinking the cans were touched at one point another. I had workers up at the site and since then the repeater has not been working to good.. this is the reason for my Question about the desense.. Brent - Original Message - From: Kevin Custer [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, March 21, 2005 8:25 PM Subject: Re: [Repeater-Builder] Desense im guessing? Brent wrote: One of my 2m repeater has a problem. It is a GE Mastr II base/repeater. have a set of wacom WP-639 on the machine, and a ARR preamp. ..a user 2 air miles fromt he site is wiped out of the receiver while the Tx is On, I turn the PA down below 20watts and he ( or all users) are clear. I have tried two different antennas before thinking about the duplexers, and want to double check other options before the cans.. these were factory tuned..cans. any thought or suggestions Not enough duplexer. For a 50 to 100 watt Station with a receiver preamp you should have *at least* a WP-641, and that may not be enough unless its a PLL exciter type. Kevin Custer Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense, I'm guessing?
Brent, Although there are those who will disagree with me on this, I think your WP-639 duplexer is simply not capable of sufficiently isolating your receive and transmit frequencies. While the WP-639 may get by on a low-powered system without a preamp, you may be demanding too much in your installation. Since the operating range of a repeater is limited more by its receive capability than by its power output, it makes sense to maximize the receive capability and run the minimum output power needed. First of all, the phrase factory tuned needs to be qualified. I will readily acknowledge that the majority of big-name duplexer manufacturers have the equipment (network analyzer) and expertise (highly-trained technicians) to properly tune a duplexer exactly to your stated operating frequencies. Very often, a factory-tuned duplexer is accompanied by a rather pompous statement of the form, This duplexer has been carefully tuned on laboratory-grade equipment, and NO FURTHER TUNING IS REQUIRED. Yeah, right! Unless I drove to the plant and picked up that duplexer myself, I can guarantee that it will be jostled, dropped, and bounced around during shipment to the point that it MAY be detuned enough to adversely affect its operation. I always check duplexers, isolators, and cavity filters on my own laboratory-grade equipment before installation, and I find perhaps 30% of them needing realignment. Please understand that the detuning most likely occurred during shipment, and is not the fault of the manufacturer. Whenever you put a preamp in front of a receiver, you really should put a very narrow bandpass cavity filter in front of it. It always comes as a surprise to neophyte repeater owners that a bandpass/bandreject or BpBr duplexer has almost no bandpass action at all. The notch or reject action is the major player, and the bandpass effect is minimal if nonexistent. Moreover, nearby carriers can sail right through the duplexer and cause major desense to your receiver. When you add a preamp, you are not just opening the barn door wider, you are amplifying all of the intruders! My personal preference is for two 8 bandpass cavities set for a total of 1.0 dB insertion loss after the receive side of the duplexer, and before the RF preamplifier. Don't be tempted to use one 10 or one 8 cavity set for 1.0 dB instead of two set for 0.5 dB each; the out-of-band rejection by two cavities is much greater than one cavity by itself. This is something I learned by experience- you can believe me now, or go off and find out for yourself. Trust me, you WILL settle on a minimum of two cavities. In the present climate of terrorist activity and natural disasters, it does not make any sense to deploy a repeater system that barely gets by or is good enough for the majority of users. It makes me very proud to be a member of an Amateur Radio group that designs and installs repeater systems that are as good as, and in many cases are better and more reliable than, commercial systems operated by public safety organizations. I sincerely wish that all repeater operators felt the same way! 73, Eric Lemmon WB6FLY Brent wrote: One of my 2m repeaters has a problem. It is a GE Mastr II base/repeater. I have a set of Wacom WP-639 on the machine, and an ARR preamp. ..a user 2 air miles from the site is wiped out of the receiver while the Tx is On, I turn the PA down below 20watts and he ( or all users) are clear. I have tried two different antennas before thinking about the duplexers, and want to double check other options before the cans.. these were factory tuned..cans. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
Brent wrote: On the duplexers the specs state I should have about 1.5 db loss on the TX port... I just measured the power output into a dummy load. from just the TX'er. it is set back to 30watts out.. I then hooked the duplexers back up and measured again. I have 12 watts into the same dummy load.. with little over 3db loss I am thinking the cans were touched at one point another. I had workers up at the site and since then the repeater has not been working to good.. this is the reason for my Question about the desense.. Brent If you are sure the duplexer is tuned okay, the cable between the duplexer and transmitter needs optimized. Look at this PDF file for more info: http://www.repeater-builder.com/wacom/wp6xxVHFtuninginstructions.pdf 1.5 dB is 29%, so 30 watts reduced 1.5 dB should equal 21.3 out of the 'plexer. Kevin Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
gone to take a look,, And I am not sure the were NO NEED TO BE TUNED as Eric staid I have not looked for my self as of Yet. - Original Message - From: Kevin Custer [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, March 21, 2005 9:02 PM Subject: Re: [Repeater-Builder] Desense im guessing? Brent wrote: On the duplexers the specs state I should have about 1.5 db loss on the TX port... I just measured the power output into a dummy load. from just the TX'er. it is set back to 30watts out.. I then hooked the duplexers back up and measured again. I have 12 watts into the same dummy load.. with little over 3db loss I am thinking the cans were touched at one point another. I had workers up at the site and since then the repeater has not been working to good.. this is the reason for my Question about the desense.. Brent If you are sure the duplexer is tuned okay, the cable between the duplexer and transmitter needs optimized. Look at this PDF file for more info: http://www.repeater-builder.com/wacom/wp6xxVHFtuninginstructions.pdf 1.5 dB is 29%, so 30 watts reduced 1.5 dB should equal 21.3 out of the 'plexer. Kevin Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense, I'm guessing?
With yours and Kevins reply, I have decided to go with a set of WP-643's and not use the WP-639's, I belive this would get me going. and if I need the pre amp then i will add it along with the pass cavities. One more Quick Question, since i have the set of 639's here. what would the affect of two cans from the 639s be if added to the 643's receiver side beside the loss. Brent - Original Message - From: Eric Lemmon [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, March 21, 2005 9:01 PM Subject: Re: [Repeater-Builder] Desense, I'm guessing? Brent, Although there are those who will disagree with me on this, I think your WP-639 duplexer is simply not capable of sufficiently isolating your receive and transmit frequencies. While the WP-639 may get by on a low-powered system without a preamp, you may be demanding too much in your installation. Since the operating range of a repeater is limited more by its receive capability than by its power output, it makes sense to maximize the receive capability and run the minimum output power needed. First of all, the phrase factory tuned needs to be qualified. I will readily acknowledge that the majority of big-name duplexer manufacturers have the equipment (network analyzer) and expertise (highly-trained technicians) to properly tune a duplexer exactly to your stated operating frequencies. Very often, a factory-tuned duplexer is accompanied by a rather pompous statement of the form, This duplexer has been carefully tuned on laboratory-grade equipment, and NO FURTHER TUNING IS REQUIRED. Yeah, right! Unless I drove to the plant and picked up that duplexer myself, I can guarantee that it will be jostled, dropped, and bounced around during shipment to the point that it MAY be detuned enough to adversely affect its operation. I always check duplexers, isolators, and cavity filters on my own laboratory-grade equipment before installation, and I find perhaps 30% of them needing realignment. Please understand that the detuning most likely occurred during shipment, and is not the fault of the manufacturer. Whenever you put a preamp in front of a receiver, you really should put a very narrow bandpass cavity filter in front of it. It always comes as a surprise to neophyte repeater owners that a bandpass/bandreject or BpBr duplexer has almost no bandpass action at all. The notch or reject action is the major player, and the bandpass effect is minimal if nonexistent. Moreover, nearby carriers can sail right through the duplexer and cause major desense to your receiver. When you add a preamp, you are not just opening the barn door wider, you are amplifying all of the intruders! My personal preference is for two 8 bandpass cavities set for a total of 1.0 dB insertion loss after the receive side of the duplexer, and before the RF preamplifier. Don't be tempted to use one 10 or one 8 cavity set for 1.0 dB instead of two set for 0.5 dB each; the out-of-band rejection by two cavities is much greater than one cavity by itself. This is something I learned by experience- you can believe me now, or go off and find out for yourself. Trust me, you WILL settle on a minimum of two cavities. In the present climate of terrorist activity and natural disasters, it does not make any sense to deploy a repeater system that barely gets by or is good enough for the majority of users. It makes me very proud to be a member of an Amateur Radio group that designs and installs repeater systems that are as good as, and in many cases are better and more reliable than, commercial systems operated by public safety organizations. I sincerely wish that all repeater operators felt the same way! 73, Eric Lemmon WB6FLY Brent wrote: One of my 2m repeaters has a problem. It is a GE Mastr II base/repeater. I have a set of Wacom WP-639 on the machine, and an ARR preamp. ..a user 2 air miles from the site is wiped out of the receiver while the Tx is On, I turn the PA down below 20watts and he ( or all users) are clear. I have tried two different antennas before thinking about the duplexers, and want to double check other options before the cans.. these were factory tuned..cans. Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense, I'm guessing?
For those who may not have the Wacom catalog handy, the WP-643 duplexer comprises six 8 cavities that are rated at 102 dB isolation at 600 kHz spacing, with 2.2 dB insertion loss. Four of the cavities are BpBr, and two are bandpass only. The WP-639 duplexer comprises four 5 BpBr cavities that are rated at 80 dB isolation at 600 kHz spacing, with 1.5 dB insertion loss. Needless to say, the WP-643 is vastly superior to the WP-639 at 2m spacing. You could use two of the WP-639 cavities for bandpass application, if you replaced the single BpBr coupling loop with two Bp loops on each cavity. Try the WP-643 in stock form first. 73, Eric Lemmon WB6FLY Brent wrote: With yours and Kevin's reply, I have decided to go with a set of WP-643s and not use the WP-639s. I believe this would get me going, and if I need the pre-amp, then I will add it along with the pass cavities. One more quick question: Since I have the set of 639s here, what would the effect of two cans from the 639s be if added to the 643's receiver side- besides the loss? Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
Try adding a 10 dB pad AFTER the preamp. Should not affect sensitivity but may help your desense. AAR preamp has more gain than necessary. Dave Baughn Director of Engineering The University of Alabama Center for Public Television and Radio Box 870150 Tuscaloosa, Alabama 35487 205.348.8622 cell 205-310-8798 NEW EMAIL [EMAIL PROTECTED] [EMAIL PROTECTED] 03/21/05 07:51PM One of my 2m repeater has a problem. It is a GE Mastr II base/repeater. have a set of wacom WP-639 on the machine, and a ARR preamp. ..a user 2 air miles fromt he site is wiped out of the receiver while the Tx is On, I turn the PA down below 20watts and he ( or all users) are clear. I have tried two different antennas before thinking about the duplexers, and want to double check other options before the cans.. these were factory tuned..cans. any thought or suggestions Thanks Brent -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense, I'm guessing?
Will do! Gone with just the Wp-643's nothing else. Thanks again for the info and of course the RPTIP info. which if I read or not I tend to always miss what im looking for. 73's Brent - Original Message - From: Eric Lemmon [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, March 21, 2005 9:59 PM Subject: Re: [Repeater-Builder] Desense, I'm guessing? For those who may not have the Wacom catalog handy, the WP-643 duplexer comprises six 8 cavities that are rated at 102 dB isolation at 600 kHz spacing, with 2.2 dB insertion loss. Four of the cavities are BpBr, and two are bandpass only. The WP-639 duplexer comprises four 5 BpBr cavities that are rated at 80 dB isolation at 600 kHz spacing, with 1.5 dB insertion loss. Needless to say, the WP-643 is vastly superior to the WP-639 at 2m spacing. You could use two of the WP-639 cavities for bandpass application, if you replaced the single BpBr coupling loop with two Bp loops on each cavity. Try the WP-643 in stock form first. 73, Eric Lemmon WB6FLY Brent wrote: With yours and Kevin's reply, I have decided to go with a set of WP-643s and not use the WP-639s. I believe this would get me going, and if I need the pre-amp, then I will add it along with the pass cavities. One more quick question: Since I have the set of 639s here, what would the effect of two cans from the 639s be if added to the 643's receiver side- besides the loss? Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense, I'm guessing?
My experience so far is that the ARR preamps are terrible, very poor ability to not oscillate or overload when around any high RF field, we use only TXRX amps. So far, threw out 4 of the UHF ARR amps they make that were on repeaters. Even 100db pass/rej. duplexers don't seem to allow the amps to work correctly. lance N2HBA - Original Message - From: Brent [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, March 21, 2005 11:04 PM Subject: Re: [Repeater-Builder] Desense, I'm guessing? Will do! Gone with just the Wp-643's nothing else. Thanks again for the info and of course the RPTIP info. which if I read or not I tend to always miss what im looking for. 73's Brent - Original Message - From: Eric Lemmon [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, March 21, 2005 9:59 PM Subject: Re: [Repeater-Builder] Desense, I'm guessing? For those who may not have the Wacom catalog handy, the WP-643 duplexer comprises six 8 cavities that are rated at 102 dB isolation at 600 kHz spacing, with 2.2 dB insertion loss. Four of the cavities are BpBr, and two are bandpass only. The WP-639 duplexer comprises four 5 BpBr cavities that are rated at 80 dB isolation at 600 kHz spacing, with 1.5 dB insertion loss. Needless to say, the WP-643 is vastly superior to the WP-639 at 2m spacing. You could use two of the WP-639 cavities for bandpass application, if you replaced the single BpBr coupling loop with two Bp loops on each cavity. Try the WP-643 in stock form first. 73, Eric Lemmon WB6FLY Brent wrote: With yours and Kevin's reply, I have decided to go with a set of WP-643s and not use the WP-639s. I believe this would get me going, and if I need the pre-amp, then I will add it along with the pass cavities. One more quick question: Since I have the set of 639s here, what would the effect of two cans from the 639s be if added to the 643's receiver side- besides the loss? Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense, I'm guessing?
At 11:28 PM 3/21/2005 -0500, you wrote: My experience so far is that the ARR preamps are terrible, very poor ability to not oscillate or overload when around any high RF field, we use only TXRX amps. So far, threw out 4 of the UHF ARR amps they make that were on repeaters. Even 100db pass/rej. duplexers don't seem to allow the amps to work correctly. --- I swear by AngleLinear preamps in all my receiver needs. No one else even comes close to Chip's equipment... Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html We now offer complete Kenwood TKR repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense im guessing?
At 06:48 PM 3/21/05, you wrote: On the duplexers the specs state I should have about 1.5 db loss on the TX port... I just measured the power output into a dummy load. from just the TX'er. it is set back to 30watts out.. I then hooked the duplexers back up and measured again. I have 12 watts into the same dummy load.. with little over 3db loss I am thinking the cans were touched at one point another. I had workers up at the site and since then the repeater has not been working to good.. One of the things I do is that after everything is working properly I put a drop of Locktite on each mechanical adjustment: helicals, cavities, duplexers, etc. I use the stuff that cracks and flakes off. Then if something has been touched, it's visible. Mike WA6ILQ Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense Problems
--- Yahoo! Groups Survey --~-- Please help us to improve Yahoo! Groups. Take the survey now! http://v2.decipherinc.com/survey/yahoo/yah04021?list=2 ~- What kind of feedline, and cables connect everything together? - Original Message - From: Scott [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Cc: Scott [EMAIL PROTECTED] Sent: Friday, December 10, 2004 10:51 AM Subject: [Repeater-Builder] Desense Problems Hi AllI've got an installation here where I have three 2 meter antennas and a 2 meter repeater that will only operate on one of them without serious desense. The antennas are a simple J pole, a Hustler G7 ---144 and a small triband vertical. I know that none of these have much to offer and I am now in the market for a proper commercial repeater antenna but just the same, what is my problem?-only the J pole works acceptably. VSWR on all antennas using the repeater signal reads unity or very close to it between duplexer and antenna feed line, distant transmitt signal strength measurement sees the Hustler a bit stronger and they all receive a distant weak signal (repeater transmitter off) about the same (maybe the Hustler is a bit better). What I'm saying here is that all three antennas seem to work about right for what they are except that I get serious desense on two of them---30 watt transmitter, a two stage isolator in place, 6 can P-D duplexer and about 20 watts into the antennas no duplexer tuning between antenna changes. Thanks! Scott, N6NXI Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense Problems
--- Yahoo! Groups Survey --~-- Please help us to improve Yahoo! Groups. Take the survey now! http://v2.decipherinc.com/survey/yahoo/yah04021?list=2 ~- Good question--- The Hustler is via 1/2 heliax, the other two are 9913 or LMR-400 or maybe one of eachI'll have to look later today when I get over to the site. It's all on the roof of a 6 floor Hospital-super intermod city! The Hustler was installed as the repeater antennathe other two are normally used for remote base linkingI'm aware of the general no-no concerning foil coax's in duplex service. Thanks Mathew, Scott - Original Message - From: Mathew Quaife [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Friday, December 10, 2004 10:57 AM Subject: Re: [Repeater-Builder] Desense Problems What kind of feedline, and cables connect everything together? - Original Message - From: Scott [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Cc: Scott [EMAIL PROTECTED] Sent: Friday, December 10, 2004 10:51 AM Subject: [Repeater-Builder] Desense Problems Hi AllI've got an installation here where I have three 2 meter antennas and a 2 meter repeater that will only operate on one of them without serious desense. The antennas are a simple J pole, a Hustler G7 ---144 and a small triband vertical. I know that none of these have much to offer and I am now in the market for a proper commercial repeater antenna but just the same, what is my problem?-only the J pole works acceptably. VSWR on all antennas using the repeater signal reads unity or very close to it between duplexer and antenna feed line, distant transmitt signal strength measurement sees the Hustler a bit stronger and they all receive a distant weak signal (repeater transmitter off) about the same (maybe the Hustler is a bit better). What I'm saying here is that all three antennas seem to work about right for what they are except that I get serious desense on two of them---30 watt transmitter, a two stage isolator in place, 6 can P-D duplexer and about 20 watts into the antennas no duplexer tuning between antenna changes. Thanks! Scott, N6NXI Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense Problems
How does the repeater act into a dummy load or service monitor?? something that u know how a good or proper 50ohm load.. Brent - Original Message - From: Scott [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Cc: Scott [EMAIL PROTECTED] Sent: Friday, December 10, 2004 12:51 PM Subject: [Repeater-Builder] Desense Problems Hi AllI've got an installation here where I have three 2 meter antennas and a 2 meter repeater that will only operate on one of them without serious desense. The antennas are a simple J pole, a Hustler G7 ---144 and a small triband vertical. I know that none of these have much to offer and I am now in the market for a proper commercial repeater antenna but just the same, what is my problem?-only the J pole works acceptably. VSWR on all antennas using the repeater signal reads unity or very close to it between duplexer and antenna feed line, distant transmitt signal strength measurement sees the Hustler a bit stronger and they all receive a distant weak signal (repeater transmitter off) about the same (maybe the Hustler is a bit better). What I'm saying here is that all three antennas seem to work about right for what they are except that I get serious desense on two of them---30 watt transmitter, a two stage isolator in place, 6 can P-D duplexer and about 20 watts into the antennas no duplexer tuning between antenna changes. Thanks! Scott, N6NXI Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense
NO I will be sending the Weather Warning on the Mur . For the Family that have their children at the parks etc. If that's your real reason... Take the weather radio out of the repeater cabinet, down to the park, and plug it into a decent audio PA and a loudspeaker and set it in Alert mode. You'll have the added comfort of saving the lives of poor families with children that don't have the money to be able to buy MURS radios. And you'll have less struggle shielding it from the repeater(s). And just think! NWS RF engineers went through all that trouble to set up decent coverage patterns and lots of transmitters in town just so people at the park could receive the signal. Amazing. Almost like they planned it or something. What will they think of next? $10 WeatherRadios at Radio Shack? I can hardly wait! ;-) (Heh heh...) Nate WY0X (Sorry Don, your sob story about the families with children at parks had me laughing out loud... families that can afford to outfit everyone with MURS radios, but can't think far enough ahead to go inside when it's raining, look at a weather forecast at least once a day, leave a commercial broadcast radio on in the background (EBS), or buy a WeatherRadio... and are so clueless that you have to rescue them with illegal MURS broadcasts from NWS. That's rich. I was laughing hard enough that it hurt on that one! Maybe they need to enroll the kids in Scouting instead of Little League. Then maybe the kids will take care of Mom and Dad and bring the rain ponchos for them too.) Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense
At 06:26 PM 6/1/2004 -0500, you wrote: Then tie that into My 440 repeater that I rebroadcast the NWS and Amber Alert Warnings . well the Testing I have done The Two Watts . De sensed the Weather receiver so bad It distorts the signal which is a strong one on a homemade outside ant at 20 Ft. 151.82 is also a homemade ant at 30 Ft. opposite side of QTH. ---Well you know what they say about the best desense is a good offense! As crummy as cheap WX receivers seem to be, it seems hard to believe that 2 watts, 20 feet away from a radio that is more than 10 megs away, is the culprit. Are you sure it's not a case of the 2 watt radio being in close enough proximity to the WX radio itself so as to simply be blocking it? Ya know.. plastic case and all? Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html AH6LE/R - IRLP Node 3000 http://www.irlp.net Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense
I hope you are not talking about re-broadcasting MURS on any other bands or a repeater on MURS? None of that is allowed, period. Ron -Original Message- From: Don [mailto:[EMAIL PROTECTED] Sent: Tuesday, June 01, 2004 4:26 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense I have a lot of Non Ham friends who use the Mur Freq 151.820 taking their HT To Little League Games Camping Etc , And I was going to set up a Legal 2 Watt Narrow/band FCC type accepted Radio , Whew had to get that out of the way first. Then tie that into My 440 repeater that I rebroadcast the NWS and Amber Alert Warnings . well the Testing I have done The Two Watts . De sensed the Weather receiver so bad It distorts the signal which is a strong one on a homemade outside ant at 20 Ft. 151.82 is also a homemade ant at 30 Ft. opposite side of QTH. Can I use some kind of Filter on the 162.425 Receiver to knock this down . In case No one knows about the Lic Free Murs Band http://www.provide.net/~prsg/murs_faq.htm We use it a lot in My area to bring Hams and Non Hams and people Interested in Communications together lots of radios in wife cars Etc. Thanks Don KA9QJG Yahoo! Groups Links FREE spam killer: http://eliminatespam.com * FREE PopUp Buster+: http://popupbuster.net Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/ attachment: winmail.dat
RE: [Repeater-Builder] Desense
At 04:55 PM 6/1/04 -0700, you wrote: I hope you are not talking about re-broadcasting MURS on any other bands or a repeater on MURS? None of that is allowed, period. Ron I know the Rules I posted the info in Case this came up, NO I will be sending the Weather Warning on the Mur . For the Family that have their children at the parks etc. Just forget it , I just ask a simple question about desense, I don't want to start a big thread about legal this and that , I thought My intentions were clear, but I guess not Sorry 73 Thanks Don KA9QJG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense
Don- I would be looking for the real problem. I have done similar things. If you have a decent signal from NWS and the transmit antenna isn't right next to the receiver, you shouldn't have a problem. Try putting that receiver in a shielded box. Don [EMAIL PROTECTED] wrote: I have a lot of Non Ham friends who use the Mur Freq 151.820 taking their HT To Little League Games Camping Etc , And I was going to set up a Legal 2 Watt Narrow/band FCC type accepted Radio , Whew had to get that out of the way first. Then tie that into My 440 repeater that I rebroadcast the NWS and Amber Alert Warnings . well the Testing I have done The Two Watts . De sensed the Weather receiver so bad It distorts the signal which is a strong one on a homemade outside ant at 20 Ft. 151.82 is also a homemade ant at 30 Ft. opposite side of QTH. Can I use some kind of Filter on the 162.425 Receiver to knock this down . In case No one knows about the Lic Free Murs Band http://www.provide.net/~prsg/murs_faq.htm We use it a lot in My area to bring Hams and Non Hams and people Interested in Communications together lots of radios in wife cars Etc. Thanks Don KA9QJG Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense
You better check the rules...there is an exemption in the rules to allow rebroadcast of NWS alerts on Amateur radio, but I don't see any to allow it on MURS. Gregg R. Lengling, W9DHI, Retired Administrator http://www.milwaukeehdtv.org K2/100 S#3075 KX1 S# 57 Member: ARRL, RSGB, RCA, WERA and ORC -Original Message- From: Don [mailto:[EMAIL PROTECTED] Sent: Tuesday, June 01, 2004 6:26 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense I have a lot of Non Ham friends who use the Mur Freq 151.820 taking their HT To Little League Games Camping Etc , And I was going to set up a Legal 2 Watt Narrow/band FCC type accepted Radio , Whew had to get that out of the way first. Then tie that into My 440 repeater that I rebroadcast the NWS and Amber Alert Warnings . well the Testing I have done The Two Watts . De sensed the Weather receiver so bad It distorts the signal which is a strong one on a homemade outside ant at 20 Ft. 151.82 is also a homemade ant at 30 Ft. opposite side of QTH. Can I use some kind of Filter on the 162.425 Receiver to knock this down . In case No one knows about the Lic Free Murs Band http://www.provide.net/~prsg/murs_faq.htm We use it a lot in My area to bring Hams and Non Hams and people Interested in Communications together lots of radios in wife cars Etc. Thanks Don KA9QJG Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense
Don, It's a coincidence that I am adding a WX-1000 weather receiver/alarm system to one of my 2m repeaters, and I found that the 2m signal was clobbering the WX unit. Even moving the WX receive antenna away from and behind (it's directional) the 2m antenna didn't help. The solution was to connect a small Sinclair preselector in front of the WX receiver. These little gems are about five inches square, and have four helical resonators. I tuned it to the WX frequency, and eliminated the 2m interference. Preselectors are not cheap, but DCI will make you a nifty filter, similar to the ones for 2m, that passes just the NWS frequencies. It'll cost about $100, since it's a custom model. 73, Eric Lemmon WB6FLY Don wrote: I have a lot of Non Ham friends who use the Mur Freq 151.820 taking their HT To Little League Games Camping Etc , And I was going to set up a Legal 2 Watt Narrow/band FCC type accepted Radio , Whew had to get that out of the way first. Then tie that into My 440 repeater that I rebroadcast the NWS and Amber Alert Warnings . well the Testing I have done The Two Watts . De sensed the Weather receiver so bad It distorts the signal which is a strong one on a homemade outside ant at 20 Ft. 151.82 is also a homemade ant at 30 Ft. opposite side of QTH. Can I use some kind of Filter on the 162.425 Receiver to knock this down . In case No one knows about the Lic Free Murs Band http://www.provide.net/~prsg/murs_faq.htm We use it a lot in My area to bring Hams and Non Hams and people Interested in Communications together lots of radios in wife cars Etc. Thanks Don KA9QJG Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense
pull a set of helicals out of a Micor mobile. a high split will do fine. If you need to locate some contact me off the list. Kevin -Original Message- From: Eric Lemmon [mailto:[EMAIL PROTECTED] Sent: Tuesday, June 01, 2004 8:14 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense Don, It's a coincidence that I am adding a WX-1000 weather receiver/alarm system to one of my 2m repeaters, and I found that the 2m signal was clobbering the WX unit. Even moving the WX receive antenna away from and behind (it's directional) the 2m antenna didn't help. The solution was to connect a small Sinclair preselector in front of the WX receiver. These little gems are about five inches square, and have four helical resonators. I tuned it to the WX frequency, and eliminated the 2m interference. Preselectors are not cheap, but DCI will make you a nifty filter, similar to the ones for 2m, that passes just the NWS frequencies. It'll cost about $100, since it's a custom model. 73, Eric Lemmon WB6FLY Don wrote: I have a lot of Non Ham friends who use the Mur Freq 151.820 taking their HT To Little League Games Camping Etc , And I was going to set up a Legal 2 Watt Narrow/band FCC type accepted Radio , Whew had to get that out of the way first. Then tie that into My 440 repeater that I rebroadcast the NWS and Amber Alert Warnings . well the Testing I have done The Two Watts . De sensed the Weather receiver so bad It distorts the signal which is a strong one on a homemade outside ant at 20 Ft. 151.82 is also a homemade ant at 30 Ft. opposite side of QTH. Can I use some kind of Filter on the 162.425 Receiver to knock this down . In case No one knows about the Lic Free Murs Band http://www.provide.net/~prsg/murs_faq.htm We use it a lot in My area to bring Hams and Non Hams and people Interested in Communications together lots of radios in wife cars Etc. Thanks Don KA9QJG Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense
Or a Motrac, Motran, Mocom-70, etc. The 160-170mhz radios are essentially doorstops, or parts sources. The front end helical assembly works fine for this. Mike At 10:06 PM 6/1/04 -0400, you wrote: pull a set of helicals out of a Micor mobile. a high split will do fine. If you need to locate some contact me off the list. Kevin -Original Message- From: Eric Lemmon [mailto:[EMAIL PROTECTED] Sent: Tuesday, June 01, 2004 8:14 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense Don, It's a coincidence that I am adding a WX-1000 weather receiver/alarm system to one of my 2m repeaters, and I found that the 2m signal was clobbering the WX unit. Even moving the WX receive antenna away from and behind (it's directional) the 2m antenna didn't help. The solution was to connect a small Sinclair preselector in front of the WX receiver. These little gems are about five inches square, and have four helical resonators. I tuned it to the WX frequency, and eliminated the 2m interference. Preselectors are not cheap, but DCI will make you a nifty filter, similar to the ones for 2m, that passes just the NWS frequencies. It'll cost about $100, since it's a custom model. 73, Eric Lemmon WB6FLY Don wrote: I have a lot of Non Ham friends who use the Mur Freq 151.820 taking their HT To Little League Games Camping Etc , And I was going to set up a Legal 2 Watt Narrow/band FCC type accepted Radio , Whew had to get that out of the way first. Then tie that into My 440 repeater that I rebroadcast the NWS and Amber Alert Warnings . well the Testing I have done The Two Watts . De sensed the Weather receiver so bad It distorts the signal which is a strong one on a homemade outside ant at 20 Ft. 151.82 is also a homemade ant at 30 Ft. opposite side of QTH. Can I use some kind of Filter on the 162.425 Receiver to knock this down . In case No one knows about the Lic Free Murs Band http://www.provide.net/~prsg/murs_faq.htm We use it a lot in My area to bring Hams and Non Hams and people Interested in Communications together lots of radios in wife cars Etc. Thanks Don KA9QJG Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
