Re: [Repeater-Builder] Poor Repeater RX
put the TX into a dummy load and see if the RX gets better. If it does not try the rx into the preamp and to the rx on the repeater still dummy load on TX and see if any of that helps. let me know. also what is the reflected power on the unit? thanks John - Original Message - From: "Alexander Tubonjic" <[EMAIL PROTECTED]> To: Sent: Friday, May 20, 2005 10:18 PM Subject: [Repeater-Builder] Poor Repeater RX > Hello, > Well here is one that cant be figured out locally, thought I would > throw it to the experts. My high school radio club has recently made a > few upgrades to our VHF repeater. We replaced the Ringo Ranger antenna > with a Comet GP-9 Antenna, replaced the 9913 coax with Andrews 1/2'' > Heliax, and put a Mirage Pream inline. The problem we are having is > mainly with the preamp (I think) > I will describe the setup and give all the specs first. The repeater > Rx and Tx is from a 110 Watt Motorola Mitrek power out from the Mitrek > is 50 watts. The power supply is an Astron RS-70M, Duplexer is a > Sinclair Q202G (yes, it is properly tuned and working as it should) > the antenna is rooftop on the schools theater building (the roof is > about 75 feet AGL and the antenna is on an 8' mast pipe) there are no > obstructions for at least 5 miles around. The preamp setup is as > follows, it is after the duplexers and before the reciever. We have > the preamp directly connected into the duplexer and a jumper going > from the preamp to the Rx bulkhead on the repeater cabinet. The preamp > has two settings, a higher gain and a lower gain setting, initially we > had it setup to the higher gain setting but I went up today and > switched over to lower gain and turned the power output to 30 watts. > The problem we have is the Rx is not what is should be. It is a tad > worse then when we were running the repeater at 15 watts without the > Preamp. I would really like to get the preamp to work like it should > in the repeater system, I just dont have any ideas on what to do next > to get better sensitivity on the machine. Any thoughts and ideas would > be appreciated. Thanks. >Alexander KG4OGN > > P.s, all jumpers are made with double shielded ridgid coax, so thats > not the cause of the problem. > > > > > > > > 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] Poor Repeater RX
Is the preamp in a shielded box? Is the power to the preamp via a feedthrough capacitor? How does the repeater perform without the preamp? What does the transmitter look like on a spectrum analyzer? How does the repeater work with a simple 1/4 wavelength vertical? Is all of the cable going into the duplexer, from both the transmitter and the receiver, double shielded (RG-214/U or better)? The MITREK shares a common board between transmitter and receiver making duplexing difficult without desense. HOw does the repeater perform using a second MITREK as the receiver? Some ideas as to where to look. Hope you find the problem. 73 Glenn WB4UIV At 10:18 PM 05/20/05, you wrote: > Hello, > Well here is one that cant be figured out locally, thought I would >throw it to the experts. My high school radio club has recently made a >few upgrades to our VHF repeater. We replaced the Ringo Ranger antenna >with a Comet GP-9 Antenna, replaced the 9913 coax with Andrews 1/2'' >Heliax, and put a Mirage Pream inline. The problem we are having is >mainly with the preamp (I think) > I will describe the setup and give all the specs first. The repeater >Rx and Tx is from a 110 Watt Motorola Mitrek power out from the Mitrek >is 50 watts. The power supply is an Astron RS-70M, Duplexer is a >Sinclair Q202G (yes, it is properly tuned and working as it should) >the antenna is rooftop on the schools theater building (the roof is >about 75 feet AGL and the antenna is on an 8' mast pipe) there are no >obstructions for at least 5 miles around. The preamp setup is as >follows, it is after the duplexers and before the reciever. We have >the preamp directly connected into the duplexer and a jumper going >from the preamp to the Rx bulkhead on the repeater cabinet. The preamp >has two settings, a higher gain and a lower gain setting, initially we >had it setup to the higher gain setting but I went up today and >switched over to lower gain and turned the power output to 30 watts. > The problem we have is the Rx is not what is should be. It is a tad >worse then when we were running the repeater at 15 watts without the >Preamp. I would really like to get the preamp to work like it should >in the repeater system, I just dont have any ideas on what to do next >to get better sensitivity on the machine. Any thoughts and ideas would >be appreciated. Thanks. > Alexander KG4OGN > > P.s, all jumpers are made with double shielded ridgid coax, so thats >not the cause of the problem. > > > > > > > >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] Poor Repeater RX
Easy Fix, Get better duplexers, TX/RX are a good start. Takes mansize cans to support a preamp. TX/RX duplexers will provide the channel separation you will need for a preamp, but you still need a selective receiver to go with it. I believe the Mitrek has the selectivity you need. Also while I'm on it, your common ham preamp will probably not give you the performance you are looking for. Not only will it amplify the signal, but also amplifies the noise floor. In my years of search for the perfect preamp, I discovered the only good one says Motorola on it. You don't need 30 db, just 6 or so to greatly increase performance. Also change the antenna, the little connection in the GP-9 antenna that holds the different sections together is a prime candidate for static desense. The connector will suffer from corrosion within weeks after you put it up. It's not noticeable to the naked eye, but it is there. Buy yourself a good commercial grade antenna, DB products for instance. Look at it this way, you'll change that GP-9 antenna at a minimum of yearly. After about 4 years you'll have had a new DB products antenna paid for. In closing, sounds like you are concerned how your repeater receives, you are to be commended, many hams just want their repeater to broadcast as far as it can and who cares how it receives. All the above suggestions I have made to you, are all mistakes I have made, and learned from. Don KI0EO > > 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] Poor Repeater RX
Alexander, I ran your system's numbers through CommShop to see what kind of isolation your duplexer must have to show no desense, and I came up with 92 dB. The Sinclair Q-202G duplexer can barely make 85 dB when tuned on a network analyzer, so that's the major part of your desense problem. It's only a four-cavity duplexer, specified at 80 dB minimum isolation, so no amount of tuning is going to make it operate at an isolation above its design limit. Assuming that every bit of the interconnecting cable is double-shielded, the repeater might work properly if the preamp were preceded by a two-cavity bandpass filter. The Sinclair Q-202G duplexer, like most BpBr designs, has practically no bandpass effect, so the preamp is amplifying a whole spectrum of noise along with the desired signal. One of the less-obvious sources of noise and signal leakage is the use of UHF (PL-259) connectors in place of type N connectors, and the use of adapters and barrel or bulkhead connectors. I strongly suggest that jumper cables be made up in single lengths with the proper connectors on each end. It may be instructive to measure the noise floor at your repeater site, using the techniques described on the Repeater-Builder site. If your site has a high noise floor, you may not be able to operate a 2m repeater without some specialized design changes. Finally, you might try placing a high-quality 6dB or 10dB attenuator on the output of your preamp. Some preamps have far too much gain at VHF, and limiting the gain to no more than 12 or 15 dB sometimes makes a world of difference. 73, Eric Lemmon WB6FLY Alexander Tubonjic wrote: > Hello, > Well here is one that can't be figured out locally, thought I would > throw it to the experts. My high school radio club has recently made a > few upgrades to our VHF repeater. We replaced the Ringo Ranger antenna > with a Comet GP-9 Antenna, replaced the 9913 coax with Andrew 1/2'' > Heliax, and put a Mirage Preamp inline. The problem we are having is > mainly with the preamp (I think) > I will describe the setup and give all the specs first. The repeater > Rx and Tx is from a 110 Watt Motorola Mitrek power out from the Mitrek > is 50 watts. The power supply is an Astron RS-70M, Duplexer is a > Sinclair Q202G (yes, it is properly tuned and working as it should) > the antenna is rooftop on the schools theater building (the roof is > about 75 feet AGL and the antenna is on an 8' mast pipe) there are no > obstructions for at least 5 miles around. The preamp setup is as > follows, it is after the duplexers and before the receiver. We have > the preamp directly connected into the duplexer and a jumper going > from the preamp to the Rx bulkhead on the repeater cabinet. The preamp > has two settings, a higher gain and a lower gain setting, initially we > had it setup to the higher gain setting but I went up today and > switched over to lower gain and turned the power output to 30 watts. > The problem we have is the Rx is not what is should be. It is a tad > worse than when we were running the repeater at 15 watts without the > Preamp. I would really like to get the preamp to work like it should > in the repeater system, I just don't have any ideas on what to do next > to get better sensitivity on the machine. Any thoughts and ideas would > be appreciated. Thanks. > Alexander KG4OGN > > P.s, all jumpers are made with double shielded ridgid coax, so thats > not the cause of the problem. > > > 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] Poor Repeater RX
This has to be OT for this group but the proper conversion would be: KiloCycles per Second = KiloHertz. Unfortunately I'm old enough to remember "time before KiloHertz" . . . . or maybe its fortunate I've lived to be that old. Joe K5FOG *** REPLY SEPARATOR *** On 5/21/2005 at 9:32 PM DCFluX wrote: >I've got a kiloCycle to kiloHertz conversion table you can study. > >On 5/21/05, Richard <[EMAIL PROTECTED]> wrote: >> KiloHertz is the correct term! >> >> Richard, N7TGB >> >> >> -Original Message- >> From: Repeater-Builder@yahoogroups.com >> [mailto:[EMAIL PROTECTED] Behalf Of DCFluX >> Sent: Saturday, May 21, 2005 7:17 PM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE : Re: [Repeater-Builder] Poor Repeater RX >> >> >> Don't you mean, kiloCycles? >> >> On 5/21/05, Kevin K. Custer <[EMAIL PROTECTED]> wrote: >> > >> > >> > >> > >--- Original Message ------- >> > >From : Eric Lemmon[mailto:[EMAIL PROTECTED] >> > >Sent : 5/21/2005 4:05:15 PM >> > >To : Repeater-Builder@yahoogroups.com >> > >Cc : >> > >Subject : RE : Re: [Repeater-Builder] Poor Repeater RX >> > > >> > >Alexander, >> > > >> > >The >> > >Sinclair Q-202G duplexer can barely make 85 dB when tuned on a network >> > >analyzer, so that's the major part of your desense problem. It's only >a >> > >four-cavity duplexer, specified at 80 dB minimum isolation, so no >amount >> > >of tuning is going to make it operate at an isolation above its design >> > >limit. >> > >> > While I don't disagree with what has been written, please realize that >> > *most* commercial manufacturers 'rate' their highband/2M duplexer at >500 >> > kiloHertz split, not 600 kiloHertz where most amateur 2 meter repeaters >> are >> > operated. This added frequency separation allows for the duplexer to >> > provide more than the stated isolation at the 500 kiloHertz >specification. >> > >> > The Wacom WP-641 is specified at 85 dB of isolation at a 500 kiloHertz >> > split, but provides 93 dB of isolation at 600 kiloHertz. The Sinclair >> Q202G >> > is similar in its factory specifications, and isolation provided. >> > >> > 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 the Yahoo! Terms of Service. >> >> >> >> >> >> 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/
RE: [Repeater-Builder] Poor Repeater RX
Heh... Yes, it is interesting to have lived long enough to have seen changes, but it is also good to go along with those changes instead of staying firmly mired in the past. As I recall, the cycle-hertz change was made sometime in the 60s. Richard, N7TGB -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of Joe Jarrett Sent: Sunday, May 22, 2005 5:47 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Poor Repeater RX This has to be OT for this group but the proper conversion would be: KiloCycles per Second = KiloHertz. Unfortunately I'm old enough to remember "time before KiloHertz" . . . . or maybe its fortunate I've lived to be that old. Joe K5FOG *** REPLY SEPARATOR *** On 5/21/2005 at 9:32 PM DCFluX wrote: >I've got a kiloCycle to kiloHertz conversion table you can study. > >On 5/21/05, Richard <[EMAIL PROTECTED]> wrote: >> KiloHertz is the correct term! >> >> Richard, N7TGB >> >> >> -Original Message- >> From: Repeater-Builder@yahoogroups.com >> [mailto:[EMAIL PROTECTED] Behalf Of DCFluX >> Sent: Saturday, May 21, 2005 7:17 PM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE : Re: [Repeater-Builder] Poor Repeater RX >> >> >> Don't you mean, kiloCycles? >> >> On 5/21/05, Kevin K. Custer <[EMAIL PROTECTED]> wrote: >> > >> > >> > >> > >--- Original Message ------- >> > >From : Eric Lemmon[mailto:[EMAIL PROTECTED] >> > >Sent : 5/21/2005 4:05:15 PM >> > >To : Repeater-Builder@yahoogroups.com >> > >Cc : >> > >Subject : RE : Re: [Repeater-Builder] Poor Repeater RX >> > > >> > >Alexander, >> > > >> > >The >> > >Sinclair Q-202G duplexer can barely make 85 dB when tuned on a network >> > >analyzer, so that's the major part of your desense problem. It's only >a >> > >four-cavity duplexer, specified at 80 dB minimum isolation, so no >amount >> > >of tuning is going to make it operate at an isolation above its design >> > >limit. >> > >> > While I don't disagree with what has been written, please realize that >> > *most* commercial manufacturers 'rate' their highband/2M duplexer at >500 >> > kiloHertz split, not 600 kiloHertz where most amateur 2 meter repeaters >> are >> > operated. This added frequency separation allows for the duplexer to >> > provide more than the stated isolation at the 500 kiloHertz >specification. >> > >> > The Wacom WP-641 is specified at 85 dB of isolation at a 500 kiloHertz >> > split, but provides 93 dB of isolation at 600 kiloHertz. The Sinclair >> Q202G >> > is similar in its factory specifications, and isolation provided. >> > >> > 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 the Yahoo! Terms of Service. >> >> >> >> >> >> Yahoo! Groups Links >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> 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/
Re: [Repeater-Builder] Poor Repeater RX
Hi Joe, I haven't visited with you for several years ... Re the kilo-cycle cops vs kilo-Hertz ... http://brainerdham.org/Tips/CPS_to_Hz_conversion.html Hope this helps and 73, Neil McKie - WA6KLA Joe Jarrett wrote: > > This has to be OT for this group but the proper conversion would be: > > KiloCycles per Second = KiloHertz. > > Unfortunately I'm old enough to remember "time before KiloHertz" . . . . or > maybe its fortunate I've lived to be that old. > > Joe K5FOG > > *** REPLY SEPARATOR *** > > On 5/21/2005 at 9:32 PM DCFluX wrote: > > >I've got a kiloCycle to kiloHertz conversion table you can study. > > > >On 5/21/05, Richard <[EMAIL PROTECTED]> wrote: > >> KiloHertz is the correct term! > >> > >> Richard, N7TGB > >> > >> > >> -Original Message- > >> From: Repeater-Builder@yahoogroups.com > >> [mailto:[EMAIL PROTECTED] Behalf Of DCFluX > >> Sent: Saturday, May 21, 2005 7:17 PM > >> To: Repeater-Builder@yahoogroups.com > >> Subject: Re: RE : Re: [Repeater-Builder] Poor Repeater RX > >> > >> > >> Don't you mean, kiloCycles? > >> 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] Poor Repeater RX
Hey Guys, Well few of us played with the repeater today. We took the preamp out of line and then did the "desense test". We shut the transmitter of, opened the squelch and listened to a weak station on input of the repeater, when the transmitter was enabled I was the only one to notice any desense. It was a very minute amount. I think I am going to try the preamp route with an attenuator in line. Just thinking, what if we ran the setup like this: repeater, then band pass filter on the rx side, then preamp, then duplexer. Would that help alleviate some of the desense from the preamp? Thanks for the help. Alexander KG4OGN 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] Poor Repeater RX
At 01:34 PM 5/23/05, you wrote: >Hey Guys, > Well few of us played with the repeater today. We took the preamp >out of line and then did the "desense test". We shut the transmitter >of, opened the squelch and listened to a weak station on input of the >repeater, when the transmitter was enabled I was the only one to >notice any desense. It was a very minute amount. I think I am going to >try the preamp route with an attenuator in line. You need to put a test meter on the first limiter, and use that as your desense detector. The second limiter is also interesting to look at with weak signals. Hard numbers are always better than guessing with an uncalibrated ear. An analog VOM plugged into the test jack is all that is needed. >Just thinking, what if we ran the setup like this: repeater, then >band pass filter on the rx side, then preamp, then duplexer. Would >that help alleviate some of the desense from the preamp? you might try the sequence of antenna-duplexer-cavity-preamp-attenuator-receiver. Mike 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] Poor Repeater RX
Alexander, Not trying to be a smart A$$, but why would you put a preamp in line and then an attenuator? Kind of defeats the purpose of the preamp. What make of preamp are you using and how much gain does it have? Might want to try one with a lot less gain, I think I saw a couple postings stating that they could be had for 15 - 25 dollars. Sounds like your repeater was working great without the preamp. Also are your duplexers BpBr ? Don KI0EO Alexander Tubonjic wrote: > Hey Guys, > Well few of us played with the repeater today. We took the preamp >out of line and then did the "desense test". We shut the transmitter >of, opened the squelch and listened to a weak station on input of the >repeater, when the transmitter was enabled I was the only one to >notice any desense. It was a very minute amount. I think I am going to >try the preamp route with an attenuator in line. > Just thinking, what if we ran the setup like this: repeater, then >band pass filter on the rx side, then preamp, then duplexer. Would >that help alleviate some of the desense from the preamp? > Thanks for the help. > Alexander KG4OGN > > > > > > > >Yahoo! Groups Links > > > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Poor Repeater RX
> > Not trying to be a smart A$$, > but why would you put a preamp in line and then an attenuator? To prevent receiver overload. If the noise level received by the antenna is sufficiently high (i.e. higher than the natural thermal noise floor of the receiver/preamp), an attenuator ahead of the preamp will lower the risk of overload from strong off-channel signals *without* degrading the S/N performance of the system. Any attenuation ahead of the preamp adds directly to the noise figure of the system, so you want to keep the combined noise figure of the attenuator+preamp lower than that of the receiver would otherwise have without them if any improvement is to be realized. Or in other words, if the amount of attenuation inserted results in a noise figure that is too high, the received signal will end up having a lower S/N than it would at lower attenuation values. An attenuator after the preamp has its place too, and is often a better place to put it if the preamplifier has excessive gain, the background noise (as received by the antenna) is naturally low, and/or if there aren't any strong off-channel signals to contend with. In some cases, the best scenario is attenuation both before and after the preamp. The value of the attenuator before the preamp is chosen based on the ambient noise floor, and the one after based on how much gain is really necessary to realize any S/N improvement (i.e. to negate excessive preamp gain). Maximizing both of those to point where S/N just starts to degrade would give you the best overload protection. Noise levels will vary at a given site depending on what other emitters are keyed up, weather-related effects, "unintentional radiators" generating RFI perodically, etc., will all affect the noise floor over time. Bench tests for receiver performance with a high-gain, low-NF preamp don't give a good indication of how the system will perform when hooked up to an antenna. Selectivity (e.g. pass cavities) ahead of the preamp is almost always preferable to after it unless you're blessed with being at a site with a very low noise floor, no other strong off-channel signals to contend with, and sufficient Tx/Rx isolation to prevent overloading the preamp. Also, some preamps that aren't unconditionally stable may oscillate or act squirrelly with a high-Q filter after them. --- Jeff Jeff DePolo WN3A - [EMAIL PROTECTED] Broadcast and Communications Consultant -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.322 / Virus Database: 266.11.15 - Release Date: 5/22/2005 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] Poor Repeater RX
Alexander, That is a good start. Now you have some more work to do (sorry I didn't have a chance to comment before your trip to the site!) With the preamp OUT and repeater transmitter DISABLED, get someone to give you a weak signal (something that is far from full quieting). Now put the preamp back in line. Does the signal quieting improve substantially? If not, then you have a bad preamp, or the noise floor at your site is too high for a preamp to help you, or the preamp is being overloaded by other RF at (near) the site, or possibly the preamp is overloading your receiver. Try a bandpass cavity before the preamp and see if there is any improvement. If it passes the above test (signal is better with the preamp), then do the desense test again. Do you have more desense with the preamp in? If so, some attenuation after the preamp might help. Or it might not, depending on exactly what the problem is. As Jeff explained, some attenuation before the preamp may be helpful too, if you have a high noise floor at the site. If you have substantially more desense with the preamp than without it and adding attenuation doesn't help, your duplexer probably isn't providing adequate isolation to run with a preamp. In this case there are a number of possible configurations involving added cavities that may help. Try these tests and see what you come up with To answer your question below, the bandpass cavity will probably do more good if placed before the preamp: duplexer > bandpass cavity > preamp > receiver. Paul N1BUG On Monday 23 May 2005 04:34 pm, Alexander Tubonjic wrote: >Hey Guys, > Well few of us played with the repeater today. We took > the preamp out of line and then did the "desense test". > We shut the transmitter of, opened the squelch and > listened to a weak station on input of the repeater, when > the transmitter was enabled I was the only one to notice > any desense. It was a very minute amount. I think I am > going to try the preamp route with an attenuator in line. > Just thinking, what if we ran the setup like this: > repeater, then band pass filter on the rx side, then > preamp, then duplexer. Would that help alleviate some of > the desense from the preamp? Thanks for the help. > Alexander > KG4OGN 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] Poor Repeater RX
Jeff's excellent dissertation on adding attenuators ahead and behind preamps has been added to the following page: http://www.repeater-builder.com/rbtip/preamps.html Kevin Custer Not trying to be a smart A$$, but why would you put a preamp in line and then an attenuator? Jeff DePolo WN3A wrote: To prevent receiver overload. 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 the Yahoo! Terms of Service.
RE : Re: [Repeater-Builder] Poor Repeater RX
>--- Original Message --->From: Eric Lemmon[mailto:[EMAIL PROTECTED]>Sent: 5/21/2005 4:05:15 PM>To : Repeater-Builder@yahoogroups.com>Cc : >Subject : RE : Re: [Repeater-Builder] Poor Repeater RX> >Alexander,>>The>Sinclair Q-202G duplexer can barely make 85 dB when tuned on a network>analyzer, so that's the major part of your desense problem. It's only a>four-cavity duplexer, specified at 80 dB minimum isolation, so no amount>of tuning is going to make it operate at an isolation above its design>limit. While I don't disagree with what has been written, please realize that *most* commercial manufacturers 'rate' their highband/2M duplexer at 500 kiloHertz split, not 600 kiloHertz where most amateur 2 meter repeaters are operated. This added frequency separation allows for the duplexer to provide more than the stated isolation at the 500 kiloHertz specification. The Wacom WP-641 is specified at 85 dB of isolation at a 500 kiloHertz split, but provides 93 dB of isolation at 600 kiloHertz. The Sinclair Q202G is similar in its factory specifications, and isolation provided. 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 the Yahoo! Terms of Service.
Re: RE : Re: [Repeater-Builder] Poor Repeater RX
Don't you mean, kiloCycles? On 5/21/05, Kevin K. Custer <[EMAIL PROTECTED]> wrote: > > > > >--- Original Message --- > >From : Eric Lemmon[mailto:[EMAIL PROTECTED] > >Sent : 5/21/2005 4:05:15 PM > >To : Repeater-Builder@yahoogroups.com > >Cc : > >Subject : RE : Re: [Repeater-Builder] Poor Repeater RX > > > >Alexander, > > > >The > >Sinclair Q-202G duplexer can barely make 85 dB when tuned on a network > >analyzer, so that's the major part of your desense problem. It's only a > >four-cavity duplexer, specified at 80 dB minimum isolation, so no amount > >of tuning is going to make it operate at an isolation above its design > >limit. > > While I don't disagree with what has been written, please realize that > *most* commercial manufacturers 'rate' their highband/2M duplexer at 500 > kiloHertz split, not 600 kiloHertz where most amateur 2 meter repeaters are > operated. This added frequency separation allows for the duplexer to > provide more than the stated isolation at the 500 kiloHertz specification. > > The Wacom WP-641 is specified at 85 dB of isolation at a 500 kiloHertz > split, but provides 93 dB of isolation at 600 kiloHertz. The Sinclair Q202G > is similar in its factory specifications, and isolation provided. > > 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 the Yahoo! Terms of Service. 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: RE : Re: [Repeater-Builder] Poor Repeater RX
KiloHertz is the correct term! Richard, N7TGB -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of DCFluX Sent: Saturday, May 21, 2005 7:17 PM To: Repeater-Builder@yahoogroups.com Subject: Re: RE : Re: [Repeater-Builder] Poor Repeater RX Don't you mean, kiloCycles? On 5/21/05, Kevin K. Custer <[EMAIL PROTECTED]> wrote: > > > > >--- Original Message --- > >From : Eric Lemmon[mailto:[EMAIL PROTECTED] > >Sent : 5/21/2005 4:05:15 PM > >To : Repeater-Builder@yahoogroups.com > >Cc : > >Subject : RE : Re: [Repeater-Builder] Poor Repeater RX > > > >Alexander, > > > >The > >Sinclair Q-202G duplexer can barely make 85 dB when tuned on a network > >analyzer, so that's the major part of your desense problem. It's only a > >four-cavity duplexer, specified at 80 dB minimum isolation, so no amount > >of tuning is going to make it operate at an isolation above its design > >limit. > > While I don't disagree with what has been written, please realize that > *most* commercial manufacturers 'rate' their highband/2M duplexer at 500 > kiloHertz split, not 600 kiloHertz where most amateur 2 meter repeaters are > operated. This added frequency separation allows for the duplexer to > provide more than the stated isolation at the 500 kiloHertz specification. > > The Wacom WP-641 is specified at 85 dB of isolation at a 500 kiloHertz > split, but provides 93 dB of isolation at 600 kiloHertz. The Sinclair Q202G > is similar in its factory specifications, and isolation provided. > > 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 the Yahoo! Terms of Service. 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: RE : Re: [Repeater-Builder] Poor Repeater RX
I've got a kiloCycle to kiloHertz conversion table you can study. On 5/21/05, Richard <[EMAIL PROTECTED]> wrote: > KiloHertz is the correct term! > > Richard, N7TGB > > > -Original Message- > From: Repeater-Builder@yahoogroups.com > [mailto:[EMAIL PROTECTED] Behalf Of DCFluX > Sent: Saturday, May 21, 2005 7:17 PM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE : Re: [Repeater-Builder] Poor Repeater RX > > > Don't you mean, kiloCycles? > > On 5/21/05, Kevin K. Custer <[EMAIL PROTECTED]> wrote: > > > > > > > > >--- Original Message --- > > >From : Eric Lemmon[mailto:[EMAIL PROTECTED] > > >Sent : 5/21/2005 4:05:15 PM > > >To : Repeater-Builder@yahoogroups.com > > >Cc : > > >Subject : RE : Re: [Repeater-Builder] Poor Repeater RX > > > > > >Alexander, > > > > > >The > > >Sinclair Q-202G duplexer can barely make 85 dB when tuned on a network > > >analyzer, so that's the major part of your desense problem. It's only a > > >four-cavity duplexer, specified at 80 dB minimum isolation, so no amount > > >of tuning is going to make it operate at an isolation above its design > > >limit. > > > > While I don't disagree with what has been written, please realize that > > *most* commercial manufacturers 'rate' their highband/2M duplexer at 500 > > kiloHertz split, not 600 kiloHertz where most amateur 2 meter repeaters > are > > operated. This added frequency separation allows for the duplexer to > > provide more than the stated isolation at the 500 kiloHertz specification. > > > > The Wacom WP-641 is specified at 85 dB of isolation at a 500 kiloHertz > > split, but provides 93 dB of isolation at 600 kiloHertz. The Sinclair > Q202G > > is similar in its factory specifications, and isolation provided. > > > > 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 the Yahoo! Terms of Service. > > > > > > 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: RE : Re: [Repeater-Builder] Poor Repeater RX
At 11:32 PM 5/21/05, DCFluX wrote: >I've got a kiloCycle to kiloHertz conversion table you can study. LOL! Did that come with one for uuf to pf also? Roger Grady K9OPO 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: RE : Re: [Repeater-Builder] Poor Repeater RX
The definite writeup is at <http://www.brainerdham.org/Tips/CPS_to_Hz_conversion.html> Mike WA6ILQ At 07:36 PM 5/21/05, you wrote: >KiloHertz is the correct term! > >Richard, N7TGB > > >-Original Message- >From: Repeater-Builder@yahoogroups.com >[mailto:[EMAIL PROTECTED] Behalf Of DCFluX >Sent: Saturday, May 21, 2005 7:17 PM >To: Repeater-Builder@yahoogroups.com >Subject: Re: RE : Re: [Repeater-Builder] Poor Repeater RX > > >Don't you mean, kiloCycles? > >On 5/21/05, Kevin K. Custer <[EMAIL PROTECTED]> wrote: > > > > > > > > >--- Original Message --- > > >From : Eric Lemmon[mailto:[EMAIL PROTECTED] > > >Sent : 5/21/2005 4:05:15 PM > > >To : Repeater-Builder@yahoogroups.com > > >Cc : > > >Subject : RE : Re: [Repeater-Builder] Poor Repeater RX > > > > > >Alexander, > > > > > >The > > >Sinclair Q-202G duplexer can barely make 85 dB when tuned on a network > > >analyzer, so that's the major part of your desense problem. It's only a > > >four-cavity duplexer, specified at 80 dB minimum isolation, so no amount > > >of tuning is going to make it operate at an isolation above its design > > >limit. > > > > While I don't disagree with what has been written, please realize that > > *most* commercial manufacturers 'rate' their highband/2M duplexer at 500 > > kiloHertz split, not 600 kiloHertz where most amateur 2 meter repeaters >are > > operated. This added frequency separation allows for the duplexer to > > provide more than the stated isolation at the 500 kiloHertz specification. > > > > The Wacom WP-641 is specified at 85 dB of isolation at a 500 kiloHertz > > split, but provides 93 dB of isolation at 600 kiloHertz. The Sinclair >Q202G > > is similar in its factory specifications, and isolation provided. > > > > 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 the Yahoo! Terms of Service. > > > > > >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/
