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.
[Repeater-Builder] Re: On The Air!
Mark, That is great news. You are to be complimented for not giving up on the sometimes difficult Micor. 73, Joe - WA7JAW -- In Repeater-Builder@yahoogroups.com, n9wys [EMAIL PROTECTED] wrote: The new Joliet East GMRS repeater is ON-THE-AIR! 462.5500 PL 156.7 Thanks to everyone who assisted me with this project - whether it was with hardware, technical or moral support. ;-) Mark - WQIV271 / N9WYS
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] On The Air!
Yes it is, George. Mark - WQIV271/N9WYS (LAG 1970) -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of George Henry Is that affiliated with the LAG (Lakes Area GMRS) Group, Mark? George, KA3HSW / WQGJ413 LAG 951 - Original Message - From: n9wys [EMAIL PROTECTED] The new Joliet East GMRS repeater is ON-THE-AIR! 462.5500 PL 156.7 Thanks to everyone who assisted me with this project - whether it was with hardware, technical or moral support. ;-) Mark - WQIV271 / N9WYS
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
[Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
--- In Repeater-Builder@yahoogroups.com, Eric Lemmon [EMAIL PROTECTED] wrote: 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 I got two sets of db 4060 duplexers and checking them I found that they have han a surge into them and each set were bad but i needed a 6 can set so I took them and made a great set with about 1.7 db loss on the pass on each side with about 110 db notch had to change the piston caps on 2 of them and make sure to clean them up as much as possible btw the cables where 10 inches long on all Joel kj4si -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 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] Re: On The Air!
Thanks Joe! It certainly helps to have the correct parts! That Master Decoder card was the Achilles Heel. Once I got the correct card, it worked like a charm! wink This is why I love the hobby so much... I have NO formal electronics training - all of mine has been self-taught. Yet I was able to reconstruct and understand the operation of the station well enough to troubleshoot most of the issues and then tune-up the station myself. FWIW - photos are posted at the R-B Groups site, in a photo album labeled N9WYS Repeaters. Mark - N9WYS/WQIV271 -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Joe Burkleo Mark, That is great news. You are to be complimented for not giving up on the sometimes difficult Micor. 73, Joe - WA7JAW -- In Repeater-Builder@yahoogroups.com, n9wys [EMAIL PROTECTED] wrote: The new Joliet East GMRS repeater is ON-THE-AIR! 462.5500 PL 156.7 Thanks to everyone who assisted me with this project - whether it was with hardware, technical or moral support. ;-) Mark - WQIV271 / N9WYS Yahoo! Groups Links No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.173 / Virus Database: 270.7.6/1712 - Release Date: 10/7/2008 9:41 AM
[Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
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.
... as determined by what? Just because you can't see it
with your service monitor doesn't mean a problem isn't there.
Something different to try
Take a different radio/transmitter... maybe a lower power
level to start this test... place it on the repeater tx
frequency into the duplexer tx path. Be sure to terminate
or disable the original repeater transmitter.
Monitor the receiver, key the alternate transmitter into
the duplexer tx port.
Got Milk? Got desense?
I never did see if you stated to have a circulator/isolator in
line?
Another trick is to try both reducing tx power to near nothing
while observing the desense and to also try inserting a high
power 10 dB attenuator in the tx path to see what happens at
full and reduced power.
Moving along... we'll wait to see what you report back.
cheers,
s.
[Repeater-Builder] WTD - Moto TLN8381A Micor rx reed - 100.0
As the subject says, I'm in need of a 100.0 reed for a Micor receiver. I have a 103.5 or 156.7 to swap if that helps you any. This is the slightly larger reed than the transmit (and other equipment) uses. Please email direct. Thanks Mike/W5JR [EMAIL PROTECTED]
[Repeater-Builder] re...: duplexor specs
I have a RxTx Cavity Filter, Vari-Notch number: 15-14-01 Does anyone have any information on the capabilities of this? I've already checked Kevins site: Repeater BuilderDuplexor Specs...
RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Skipp, Please explain your first statement. if I can't see it on the spectrum analyzer, then what is it? No circulator/isolator in line during test. VSWR is indetectable between the TX and the cans. If I lower the power enough, the desense goes away. just as I'd expect. It's a matter of scale, after all. By the way. the symptoms are both the same with 2 separate repeaters (I amended my first post to say that), so unless they both have the same problems, the issue is not the with TX. Mike From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Tuesday, October 07, 2008 12:27 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables 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. ... as determined by what? Just because you can't see it with your service monitor doesn't mean a problem isn't there. Something different to try Take a different radio/transmitter... maybe a lower power level to start this test... place it on the repeater tx frequency into the duplexer tx path. Be sure to terminate or disable the original repeater transmitter. Monitor the receiver, key the alternate transmitter into the duplexer tx port. Got Milk? Got desense? I never did see if you stated to have a circulator/isolator in line? Another trick is to try both reducing tx power to near nothing while observing the desense and to also try inserting a high power 10 dB attenuator in the tx path to see what happens at full and reduced power. Moving along... we'll wait to see what you report back. cheers, s. 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] Kenwood battery back-up
At 03:44 PM 10/06/08, you wrote: Our club has recently acquired a TKR-750 and a TKR-850, to replace an aging hodgepodge of repeater components. Both the TKR's are co-located and share a Link RLC controller. We want to use the excellent battery-backup provisions of the TKR's, WHAT excellent battery backup provisions? It's a simple changeover circuit, and the Kenwood internal trickle charger is a joke. with a Wal-Mart marine battery. You'll be sorry. A marine battery is a just a starting battery - a variation on an automotive battery. You want a true deep cycle battery (think golf cart). We plan to connect the one battery to both repeaters' battery ports in parallel, but activate the charging jumper on only one repeater. I guess we just want reassurance that there are no problems with this arrangment; any comments will be appreciated! So the battery lasts half as long (powering both repeaters) and takes twice as long to recharge (being charged by one). Chappy Rice kd4ss Float the battery across a good high quality aftermarket charger that is designed to keep a standby battery alive, and maximize the life. Look at those sold for RVs and for standby generators. Warning - a GOOD charger will not be cheap. Then run the repeaters as 12v loads. Don't even hook up the AC power to them. Run the controller off the battery as well. Mike WA6ILQ
[Repeater-Builder] Re: Kenwood battery back-up
Our club has recently acquired a TKR-750 and a TKR-850, to replace an aging hodgepodge of repeater components. Both the TKR's are co-located and share a Link RLC controller. We want to use the excellent battery-backup provisions of the TKR's, with a Wal-Mart marine battery. We plan to connect the one battery to both repeaters' battery ports in parallel, but activate the charging jumper on only one repeater. I guess we just want reassurance that there are no problems with this arrangment; any comments will be appreciated! There shouldn't be any problems but you might want to consider some type of low voltage disconnect to ensure the equipment doesn't drain the battery down to an early death when the power fails (goes away) for extended periods of time. The selection and addition of a proper size diode and resistor from your power supply + terminal to the battery (direct) (+ terminal) will help more quickly recharge the battery from a depleted condition (versus trusting the trickle charge internal to the Kenwood Repeaters). The diode to prevent reverse current flow and the resistor to limit the charging current to a safe value (for the power supply capacity while still operating the repeater). The wrong selection of the resistor or direct diode to power supply wiring can kill or disable the power supply... so a little thought is required (and advise available upon request). Remember (a big deal) The Low Voltage Disconnect will save your bacon... (battery wise). cheers, s.
[Repeater-Builder] Re: Kenwood battery back-up
WHAT excellent battery backup provisions? It's a simple changeover circuit, and the Kenwood internal trickle charger is a joke. Actually it works pretty well for what it is and claims to be... a battery trickle charger. with a Wal-Mart marine battery. You'll be sorry. A marine battery is a just a starting battery - a variation on an automotive battery. You want a true deep cycle battery (think golf cart). At typical x-times the cost of a standard auto battery... I buy auto batteries and replace them after a few years of operation working well or not. Much more cost effective for the budget minded operator... and much better than having no battery backup and the dollar value is very good. So the battery lasts half as long (powering both repeaters) and takes twice as long to recharge (being charged by one). An added low voltage disconnect is a great idea. Even a single battery for short term back up is better than none. In a generator backed location it's often more than enough. There would be no reason he couldn't enable both repeater trickle charge circuits but the addition of a proper size single diode and resistor will help more quickly bring the battery back up to near full charge. Float the battery across a good high quality after-market charger that is designed to keep a standby battery alive, and maximize the life. Look at those sold for RVs and for standby generators. Warning - a GOOD charger will not be cheap. Then run the repeaters as 12v loads. Don't even hook up the AC power to them. Run the controller off the battery as well. Works as described but does cost much more money. If you already have a typical dc power supply there's no reason you can't use it with the internal Kenwood circuit. If rapid recharge of a drained battery is a major concern... add a properly sized series diode and resistor and get on with enjoying the new equipment. cheers, s.
[Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Please explain your first statement. if I can't see it on the spectrum analyzer, then what is it? Don't know until you nail down the exact cause, which a service monitor might not always clearly indicate, regardless of type and how you use it. No circulator/isolator in line during test. VSWR is indetectable between the TX and the cans. Doesn't matter... I've seen and found gremlin generation in well matched cavity and combiner systems. Especially High-Q cavities (most the larger diameter types). Telewave 8 and especially 10 inch cavities seem to be more often prone to gremlin issues when used in tx combiner and antenna systems. Other brands and cavity sizes can also crap up a system when there's a reason or cause. If I lower the power enough, the desense goes away. just as I'd expect. It's a matter of scale, after all. I would point an evil eye toward the duplexer, antenna feedline and the antenna. The obvious trick would be to swap out one or more of the mentioned until the problem goes away. By the way. the symptoms are both the same with 2 separate repeaters (I amended my first post to say that), so unless they both have the same problems, the issue is not the with TX. Are you using the same power amplifier with both repeaters? A Circulator might help you quickly locate and/or fix the problem. Type of duplexer, power amplifier, feed-line and antenna you're using? s.
[Repeater-Builder] Re: DB4060 Duplexer Cables
Good Evening Mike, I'm afraid I agree with Eric, The problems you are experiencing are not common, when you stated you moved the crystals from the Mark 4 to the spare and are experiencing the same result, was this with the same set of cans? If it was then try two mobiles on the same set of cans and check for desense that way eliminating the Mark 4 and any other Xtal rig you are using. If your desense is still there after the mobile test then you need a tracking generator to go with your spectrum analyser. That will be a start in seeing where your problem may lie. Anything more than that may be a return loss bridge and do a resonance check of the entire duplexer. If you do not have the access to the equipment, you can always try a seperate antenna on the opposite port for the duplexer to determine which side, i.e. Rx or Tx is the issue. If you have disassembled the cans and are not having much luck then the Tracking generator should show you where they are tuned and if they are really giving you a problem. By the way, what was your Sinad reading on the Rx of the Mark 4. If you are having more problems with noise than signal you may have found this in your earlier test when you swapped the Xtals and found their amplifier stage may be giving you the grief. If you swapped the Xtal in the element, versus sending it to a crystal house for overhaul, then a cold solder joint makes for all kinds of Rx fun in the form of noise. I am not 100% on the Mark 4, but if it has an Rx alignment procedure, run through that while chasing the Rx board with cold spray or a gentle tap during the test and see if your sinad changes or your performance changes. Your 8920 will show you that in the right range if you have a problem as you look at you Tx signal I hope this can help, Jason --- In Repeater-Builder@yahoogroups.com, Mike Besemer \(WM4B\) [EMAIL PROTECTED] wrote: 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'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
[Repeater-Builder] Wanted: Motorola Mitrek VHF
I am trying to find a couple of VHF Mitreks for convertion to repeater use and am having difficulty finding them locally. I have checked a few websites with no success, and am looking for suggestions on other websites that might offer these at surplus prices. Any advice appreciated. 73 de W2AFD Howard
[Repeater-Builder] racom 1300 identifier manual wanted
need information on a Racom model 1300 Morse Code Station Identifier Building a backup repeater for the K9TRC/R which is down at this time. Need: Manual Software ? interface cable ? What do I need to program this indentifier? Garry WW9GT
[Repeater-Builder] Re: DB4060 Duplexer Internal Plunger/rod cleaning.
I have been known to carefully clamp a cavity tuning rod into my hand-held (9.6v) Makita drill chuck and fairly slow-run the tuning plunger (rod) a few times through it's near entire range (end-to-end). Then retuning it to square one. In the case where I suspect pitting on the internal plunger contacts... I might try to swap the cavities across to the other side (tx to rx and the converse) so the desired plunger position is in a new spot. s. Mike Besemer \(WM4B\) [EMAIL PROTECTED] wrote: 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
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] racom 1300 identifier manual wanted
Garry W Tidler wrote: need information on a Racom model 1300 Morse Code Station Identifier Building a backup repeater for the K9TRC/R which is down at this time. Need: Manual Software ? interface cable ? What do I need to program this indentifier? Garry WW9GT Well, here's the web site for starters: http://www.racominc.com/ Its been a long time, but as I remember, all but the 1400 series were PROM based, so you would need a PROM burner. I also don't remember what type of PROM it was, other than I'm also fairly certain it was NOT an erasable EPROM. Not sure if you can still get them. But I bet the company would still do it. The 1400 series was dip-switch programmable.
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] racom 1300 identifier manual wanted
Yes Jim is correct.. 1300 needed a prom.. 1400 was dipswitch, The 1400 had the fancy features, the 1300 was stripped down to basics and offered to amateur as well as commercial.. as more of an entry level box... the newer units have pc programming if I am not mistaken, but the 1300 and 1400 predate PC's... :-) You will need to order the prom from them as there was never field info released to make your own. But the data in the prom was fairly easy to dissect if you wanted to roll your own.. assuming you have stuff to read and edit them... I used to be a tech there.. :-) Doug At 07:57 PM 10/7/2008, you wrote: Garry W Tidler wrote: need information on a Racom model 1300 Morse Code Station Identifier Building a backup repeater for the K9TRC/R which is down at this time. Need: Manual Software ? interface cable ? What do I need to program this indentifier? Garry WW9GT Well, here's the web site for starters: http://www.racominc.com/http://www.racominc.com/ Its been a long time, but as I remember, all but the 1400 series were PROM based, so you would need a PROM burner. I also don't remember what type of PROM it was, other than I'm also fairly certain it was NOT an erasable EPROM. Not sure if you can still get them. But I bet the company would still do it. The 1400 series was dip-switch programmable.
[Repeater-Builder] Re: re...: duplexor specs
--- Thankyou.. . . .. In Repeater-Builder@yahoogroups.com, Captainlance [EMAIL PROTECTED] wrote: TXRX 15/14/01 is a 38 to 50 mhz single cavity, vari-notch style. Lance N2HBA - Original Message - From: Randy To: Repeater-Builder@yahoogroups.com Sent: Tuesday, October 07, 2008 2:16 PM Subject: [Repeater-Builder] re...: duplexor specs I have a RxTx Cavity Filter, Vari-Notch number: 15-14-01 Does anyone have any information on the capabilities of this? I've already checked Kevins site: Repeater BuilderDuplexor Specs... -- No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.173 / Virus Database: 270.7.6/1711 - Release Date: 10/6/2008 5:37 PM
[Repeater-Builder] Re: Wanted: Motorola Mitrek VHF
---How many do you want? I have afew that I have'nt dismantled yet... In Repeater-Builder@yahoogroups.com, Howard [EMAIL PROTECTED] wrote: I am trying to find a couple of VHF Mitreks for convertion to repeater use and am having difficulty finding them locally. I have checked a few websites with no success, and am looking for suggestions on other websites that might offer these at surplus prices. Any advice appreciated. 73 de W2AFD Howard
[Repeater-Builder] Re: racom 1300 identifier manual wanted
---http://www.retrevo.com/s/Racom+1300?sub.x=42sub.y=15 . In Repeater-Builder@yahoogroups.com, Garry W Tidler [EMAIL PROTECTED] wrote: need information on a Racom model 1300 Morse Code Station Identifier Building a backup repeater for the K9TRC/R which is down at this time. Need: Manual Software ? interface cable ? What do I need to program this indentifier? Garry WW9GT
RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
The problem occurs into both the antenna system and the -8920 with two totally different repeaters. There is no external PA. I've already said that the duplexers are bad. they're the only common component. This is all basic troubleshooting! Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Tuesday, October 07, 2008 5:49 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Please explain your first statement. if I can't see it on the spectrum analyzer, then what is it? Don't know until you nail down the exact cause, which a service monitor might not always clearly indicate, regardless of type and how you use it. No circulator/isolator in line during test. VSWR is indetectable between the TX and the cans. Doesn't matter... I've seen and found gremlin generation in well matched cavity and combiner systems. Especially High-Q cavities (most the larger diameter types). Telewave 8 and especially 10 inch cavities seem to be more often prone to gremlin issues when used in tx combiner and antenna systems. Other brands and cavity sizes can also crap up a system when there's a reason or cause. If I lower the power enough, the desense goes away. just as I'd expect. It's a matter of scale, after all. I would point an evil eye toward the duplexer, antenna feedline and the antenna. The obvious trick would be to swap out one or more of the mentioned until the problem goes away. By the way. the symptoms are both the same with 2 separate repeaters (I amended my first post to say that), so unless they both have the same problems, the issue is not the with TX. Are you using the same power amplifier with both repeaters? A Circulator might help you quickly locate and/or fix the problem. Type of duplexer, power amplifier, feed-line and antenna you're using? s. image001.jpgimage002.jpg
RE: [Repeater-Builder] Re: DB4060 Duplexer Internal Plunger/rod cleaning.
Great minds think alike. Now that I know how to get the blasted knobs off I'm going to try that. I did swap RX and TX for that very reason and had pretty much the same problem. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Tuesday, October 07, 2008 5:58 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: DB4060 Duplexer Internal Plunger/rod cleaning. I have been known to carefully clamp a cavity tuning rod into my hand-held (9.6v) Makita drill chuck and fairly slow-run the tuning plunger (rod) a few times through it's near entire range (end-to-end). Then retuning it to square one. In the case where I suspect pitting on the internal plunger contacts... I might try to swap the cavities across to the other side (tx to rx and the converse) so the desired plunger position is in a new spot. s. Mike Besemer \(WM4B\) [EMAIL PROTECTED] wrote: 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 image001.jpgimage002.jpg
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
[Repeater-Builder] Icom repeater
Subject: Icom repeater I have 2 demo Icom FR-4000-3 repeaters for sale Will program to your GMRS channels, tones and call sign. $800.00 each and shippingFL address add sales tax. thank you, John (727) 441-3250
[Repeater-Builder] Re: Kenwood battery backup
Many thanks for all the replies and the expertise that this list is known for. Maybe excellent wasn't the best choice of words to describe the Kenwood TKR battery backup system, but here are some of the reasons why we like it: The switchover circuit and the trickle charger are builit in, there are convenient screw terminals for the battery, and there is a convenient alert tone system (although I'm not sure it works when external controllers are used). All this without cobbling up external relays, diodes, resistors, heavy-duty connectors, etc. that I've done in the past, with mixed results. I thought the Wal-Mart marine battery was meant for DC trolling motors, hence deep cycle, but we will give consideration to the golf cart bateries that many of you mentioned. The intent was to replace the battery every 3 or 4 years. I have a Wal-Mart marine battery presently in use with a commercial Kenwood TKR where I used to work. We put it in a sealed case, cut a hole and attached a 3/4 hose that runs outside. We hope that will vent most acid fumes, gasses, etc outside of the building. Our present sites have generator backup, although the generators have been known to fail when most needed. In these cases we hope the battery will keep things going until we get there to replace fuses, fix the generator, hookup our own Honda, etc. I might add that we do have Samlex 20A supplies in each repeater's cabinet. Another use of the battery-backup would be in the event that lightning disabled the Samlex's. Thanks again! Chappy kd4ss -- Our club has recently acquired a TKR-750 and a TKR-850, to replace an aging hodgepodge of repeater components. Both the TKR's are co-located and share a Link RLC controller. We want to use the excellent battery-backup provisions of the TKR's, with a Wal-Mart marine battery. We plan to connect the one battery to both repeaters' battery ports in parallel, but activate the charging jumper on only one repeater. I guess we just want reassurance that there are no problems with this arrangment; any comments will be appreciated!
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.
[Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Something I would try, which I would not recommend to others is to rotate the tuning plungers and maybe the cap(s) with the unit under power making trouble. I have used this method to find grunge makers, which turned out to be plunger pitting, capacitor problems and hydroscopic sourced breakdowns. If you try the above, reduce the tx power to the min you need to confirm grunge/desense and keep your tx keydown times to a minimum value. Don't try the above unless you're sure or willing to trust the RF PA final is a fairly rugged beast/circuit/device. I'm willing to take the mentioned test gamble in 99.5% of the more common situations. If you are smart, quick and careful... you might be able to catch the source of trouble if it has a mechanical contribution. s. Mike Besemer \(WM4B\) [EMAIL PROTECTED] wrote: The problem occurs into both the antenna system and the -8920 with two totally different repeaters. There is no external PA. I've already said that the duplexers are bad. they're the only common component. This is all basic troubleshooting! Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Tuesday, October 07, 2008 5:49 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Please explain your first statement. if I can't see it on the spectrum analyzer, then what is it? Don't know until you nail down the exact cause, which a service monitor might not always clearly indicate, regardless of type and how you use it. No circulator/isolator in line during test. VSWR is indetectable between the TX and the cans. Doesn't matter... I've seen and found gremlin generation in well matched cavity and combiner systems. Especially High-Q cavities (most the larger diameter types). Telewave 8 and especially 10 inch cavities seem to be more often prone to gremlin issues when used in tx combiner and antenna systems. Other brands and cavity sizes can also crap up a system when there's a reason or cause. If I lower the power enough, the desense goes away. just as I'd expect. It's a matter of scale, after all. I would point an evil eye toward the duplexer, antenna feedline and the antenna. The obvious trick would be to swap out one or more of the mentioned until the problem goes away. By the way. the symptoms are both the same with 2 separate repeaters (I amended my first post to say that), so unless they both have the same problems, the issue is not the with TX. Are you using the same power amplifier with both repeaters? A Circulator might help you quickly locate and/or fix the problem. Type of duplexer, power amplifier, feed-line and antenna you're using? s.
