RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
If this was basic troubleshooting then you would have found your problem. Your having a hard time as the list is long with questions. Just trying to help, --- On Tue, 10/7/08, Mike Besemer (WM4B) [EMAIL PROTECTED] wrote: From: Mike Besemer (WM4B) [EMAIL PROTECTED] Subject: RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables To: Repeater-Builder@yahoogroups.com Date: Tuesday, October 7, 2008, 8:41 PM 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:Repeater- [EMAIL PROTECTED] ups.com] 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.
[Repeater-Builder] TLE1703A Schematic / TLD5492A4 Alignment Directions
Hi all. We recently moved our Micor UHF and VHF repeaters to my home. However, the move seems to have broken the TLE1703A amp on the UHF repeater; Does anyone here have the schematic for this amp? The TLD5492A4 exciter is putting out 700mW as well which sounds a bit high. If anyone has the alignment instructions for the exciter, I'd really appreciate it.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Yep. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 11:35 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Hi Mike, I am a little confused as to how you are coupling the signal generator to the receiver. When you have the tx and rx connected to the duplexer normally and a dummy load on the output T (that would normally feed the antenna line) how are you coupling the signal generator to the receiver? Are you using an isolated T in the receive line to couple the generator in? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 8:21 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Gary, At this juncture, I'm not getting scientific about the actual desense measurement, but I can tell you it's in the ten's of dBs. At this point, I'm using Kevin's method. signal generator connected to the cans with the cans connected to the repeater normally. I set the signal generator to the point that the squelch breaks and turn the transmitter on manually. If the signal stays there. I'm happy (at this point). If not. I increase signal generator level until I keep the signal with the transmitter on. As I said. it's ten's of dBs at this point You're correct about where I'm connecting the dummy load. Again. I'm not using ANY antennas at this point. All testing is done into the -8920 and/or the dummy load. I'm confused about your last statement. I've not put a load at the end of the tee that feeds the feedline. If I do that, I can't feed signal to the receiver. If I take the TX line off the tee and put a dummy load there, there is no desense. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 8:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured
RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Skipp, Doing that produces some interesting noises in the receiver. It will go from full-quieting to complete garbage without much movement. Tapping, beating, and banging seem to have little to no effect. I think I'm going to tear them down again and reclean all the mating surfaces. I MUST have missed something. 73, Mike From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Tuesday, October 07, 2008 11:57 PM To: Repeater-Builder@yahoogroups.com Subject: [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:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of skipp025 Sent: Tuesday, October 07, 2008 5:49 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.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: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
No. it really IS basic troubleshooting. I've eliminated everything BUT the cans, and I've tried to let that be known here. Swaptronics is easy. swap out what you have duplicates of and eliminate suspects until you narrow it down to the faulty subsystem component. I spent over 20 years in the Air Force working avionics systems on and off the aircraft. doing a lot of component-level repairs, so I know how to troubleshoot. Nonetheless, these types of duplexers are new to me and have a different set of problems than you'd experience when working with MILSPEC stuff. I've received a lot of great advice here, but I think some folks are jumping in, trying to be helpful (for which I thank them) without reading the whole post and suggesting that I do stuff I've already tried. I know it's not the repeater itself because I've swapped it out. It's not the antenna system because I'm not using the antenna system. I'm gonna tear them down again and clean all the mating surfaces and triple check the fingerstock. Not much else to try. duplexers are not that mechanically complicated. it's the goofy stuff that goes on when you duplex RF that makes it challenging. Thanks, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Unimog Freightliner Sent: Tuesday, October 07, 2008 8:47 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables If this was basic troubleshooting then you would have found your problem. Your having a hard time as the list is long with questions. Just trying to help, --- On Tue, 10/7/08, Mike Besemer (WM4B) [EMAIL PROTECTED] wrote: From: Mike Besemer (WM4B) [EMAIL PROTECTED] Subject: RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables To: Repeater-Builder@yahoogroups.com Date: Tuesday, October 7, 2008, 8:41 PM 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:Repeater- [EMAIL PROTECTED] ups.com] 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
[Repeater-Builder] RB Server upgrade - associated outage.
The Repeater Builder web server is undergoing an upgrade. It will be unavailable for a while. Thanks, Kevin Custer
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
At 10/7/2008 03:03, you wrote: With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. Make sure there's an isolator on the TX. I've seen severe desense using a perfectly good, tuned duplexer because the TX didn't like the high reactance at the notch frequency, causing a lot of broadband noise to come out of the PA. If the 8920 is full duplex, I'd try a dummy load on a coupler or sampler instead just to make sure there isn't something inside it that's generating the noise. Bob NO6B
[Repeater-Builder] Re: Desense with DB4060 Duplexer
On one specific cavity or more than one? You're almost at the problem. No garbage with tapping, beating and banging is a good sign. One might guess you have some type of micro pitting and at least one hard point pitted contact on one of the mating surfaces. One or more of the metal plunger contact surfaces has a not easily viewed problem. Just cleaning might not cure it sometimes you need to replace finger stock and or have at the surfaces with the proper cleaning brush/function. You didn't say how you'd cleaned the surface in the past. I would only use a Brass or hard Stainless Steel brush to avoid embedding non same metals into the plunger or contact surface. Using a common steel wire brush is not a good idea. s. Mike Besemer \(WM4B\) [EMAIL PROTECTED] wrote: Skipp, Doing that produces some interesting noises in the receiver. It will go from full-quieting to complete garbage without much movement. Tapping, beating, and banging seem to have little to no effect. I think I'm going to tear them down again and reclean all the mating surfaces. I MUST have missed something. 73, Mike
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Just out of curiosity what power supply are you using? I've seen a fair amount of RFI from the Astron SS series.
Re: [Repeater-Builder] Re: Desense with DB4060 Duplexer
If the silver plating seems to be scratched, I have had good luck with the products that are used to silver plate circuit boards. I don't recall the product name that I used, but it was/is available from Digikey and such. I merely used fine steel wool to polish the plunger and then used the silverplating kit to re-plate it. Here is one product I ran across in a google search: http://www.cool-amp.com/cool-amp.html WARNING: The silverplating plating is NOT very thick. It won't take much to scratch it back off, but if you lube the finger stock with a conductive lube it will last longer. I have used no-ox in the past, but Cool-amps's Conducto-Lube might be a better choice. I have had no experience with it. Good luck, Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Rd Boswell, PA 15531 - Original Message - From: Kevin Custer [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 08, 2008 11:40 AM Subject: Re: [Repeater-Builder] Re: Desense with DB4060 Duplexer skipp025 wrote: You didn't say how you'd cleaned the surface in the past. I would only use a Brass or hard Stainless Steel brush to avoid embedding non same metals into the plunger or contact surface. Using a common steel wire brush is not a good idea. s. Also NEVER use an over the counter chemical treatment to clean the surfaces. Products like TARN-X are not acceptable for cleaning electronic equipment; relay contacts, duplexer guts, etc! Kevin Yahoo! Groups Links No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.173 / Virus Database: 270.7.6/1714 - Release Date: 10/8/2008 7:01 AM
Re: [Repeater-Builder] Re: Desense with DB4060 Duplexer
skipp025 wrote: You didn't say how you'd cleaned the surface in the past. I would only use a Brass or hard Stainless Steel brush to avoid embedding non same metals into the plunger or contact surface. Using a common steel wire brush is not a good idea. s. Also NEVER use an over the counter chemical treatment to clean the surfaces. Products like TARN-X are not acceptable for cleaning electronic equipment; relay contacts, duplexer guts, etc! Kevin
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. You lost me on that one. You're saying you're testing for desense by removing the tee from the antenna port of the duplexer, feeding the Tx leg of the duplexer into a dummy load, and the Rx leg gets fed by your 8920 sig gen? If that's the case, then that's not much of a test since you're no longer duplexing. You've totally isolated the Tx and Rx, so all you really know is whether or not you have in-cabinet desense (i.e. between the transmitter and receiver internally due to poor shielding or cable cross-coupling). Or maybe I'm totally misunderstanding how you're doing the desense test - if I have, please re-explain. The easiest way to do the desense test (while keeping the feedline and antenna out of the equation) is to connect the duplexer antenna port to a high-quality (low-noise) dummy load, with an iso-tee inline between the duplexer and load. Connect your 8920 sig gen to the decoupled port on the iso-tee, generate a weak signal while monitoring the repeater Rx local receiver, and key the transmitter on and off manually. If you have desense at that point, and it sounds ratty as if something is breaking down or making intermittant contact, then go do your tappin' n' wigglin' to see if you can narrow down the list of suspects. The dummy load on the 8920 RF port is OK, but I'd still be more comfortable using a good external load and isotee. Intermittant desense can sometimes be traced back to a component or solder joint in the transmitter being defective, which can manifest as arcing (however microscopic). The resulting transmitter noise may not be easily discernable on a spectrum analyzer, especially without attenuation of the carrier frequency to increase the dynamic range of the test equipment, but may still cause appreciable desense due to the broadband noise falling on the Rx frequency. Yes, half of the duplexer's job is to attenuate transmitter noise to keep it from getting to the receiver, but if a failing component causes the effective noise level to be elevated 20 or 30 dB, that's 20 or 30 dB more isolation your duplexer would need to provide to prevent desense, and often that kind of headroom doesn't exist. Have you measured the isolation of your duplexer from Tx port to Rx port with the antenna port terminated in a dummy load? What is the measured isolation at the Tx and Rx frequencies doing this test? --- Jeff WN3A
RE: [Repeater-Builder] 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? Not to step on Skipp's toes, but I think what he was getting at is that spectrum analyzers have a limited dynamic range, probably around 80 dB. So you can only see noise/spurs down as low as 80 dB below carrier. If you crank up the gain (i.e. reduce the attenuation) on the spectrum analyzer higher, you will start to overload it with the carrier unless you have something (filter) to attenuate the transmitter carrier. It's quite easy to have low-level spurs and broadband noise that aren't immediately discernable on the spectrum analyzer, yet they're still strong enough to cause you problems at sub-microvolt receive levels. If I lower the power enough, the desense goes away. just as I'd expect. It's a matter of scale, after all. Does the desense taper off as you reduce power, or does it suddenly disappear at some power level? That can be a big clue. 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. That's good information. As I mentioned in a previous post, I'd suggest trying duplex desense tests with a good external load rather than the one built into the 8920 just to rule that out too. --- Jeff WN3A
Re: [Repeater-Builder] Re: racom 1300 identifier manual wanted
Randy wrote: http://www.retrevo.com/s/Racom+1300?sub.x=42sub.y=15 Reposted so the link is clickable...
Re: [Repeater-Builder] Re: Desense with DB4060 Duplexer
Scott, a product that I have used on all kinds of connections including RF is Stabilant 22. It is made in Richmond Hill Ontario and does a wonderful job of making a good connection between metal surfaces. It is quite expensive, $35.00 for a small bottle but you only need a drop of it to work. John VE3AMZ - Original Message - From: Scott Zimmerman [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 08, 2008 11:59 AM Subject: Re: [Repeater-Builder] Re: Desense with DB4060 Duplexer If the silver plating seems to be scratched, I have had good luck with the products that are used to silver plate circuit boards. I don't recall the product name that I used, but it was/is available from Digikey and such. I merely used fine steel wool to polish the plunger and then used the silverplating kit to re-plate it. Here is one product I ran across in a google search: http://www.cool-amp.com/cool-amp.html WARNING: The silverplating plating is NOT very thick. It won't take much to scratch it back off, but if you lube the finger stock with a conductive lube it will last longer. I have used no-ox in the past, but Cool-amps's Conducto-Lube might be a better choice. I have had no experience with it. Good luck, Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Rd Boswell, PA 15531 - Original Message - From: Kevin Custer [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 08, 2008 11:40 AM Subject: Re: [Repeater-Builder] Re: Desense with DB4060 Duplexer skipp025 wrote: You didn't say how you'd cleaned the surface in the past. I would only use a Brass or hard Stainless Steel brush to avoid embedding non same metals into the plunger or contact surface. Using a common steel wire brush is not a good idea. s. Also NEVER use an over the counter chemical treatment to clean the surfaces. Products like TARN-X are not acceptable for cleaning electronic equipment; relay contacts, duplexer guts, etc! Kevin Yahoo! Groups Links No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.173 / Virus Database: 270.7.6/1714 - Release Date: 10/8/2008 7:01 AM Yahoo! Groups Links
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Jeff, I have been watching this thread and must say your explanation here is very well done. Thank you from the rest of us watching. Collin -Original Message- From: Jeff DePolo [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wed, 8 Oct 2008 1:00 pm Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. You lost me on that one. You're saying you're testing for desense by removing the tee from the antenna port of the duplexer, feeding the Tx leg of the duplexer into a dummy load, and the Rx leg gets fed by your 8920 sig gen? If that's the case, then that's not much of a test since you're no longer duplexing. You've totally isolated the Tx and Rx, so all you really know is whether or not you have in-cabinet desense (i.e. between the transmitter and receiver internally due to poor shielding or cable cross-coupling). Or maybe I'm totally misunderstanding how you're doing the desense test - if I have, please re-explain. The easiest way to do the desense test (while keeping the feedline and antenna out of the equation) is to connect the duplexer antenna port to a high-quality (low-noise) dummy load, with an iso-tee inline between the duplexer and load. Connect your 8920 sig gen to the decoupled port on the iso-tee, generate a weak signal while monitoring the repeater Rx local receiver, and key the transmitter on and off manually. If you have desense at that point, and it sounds ratty as if something is breaking down or making intermittant contact, then go do your tappin' n' wigglin' to see if you can narrow down the list of suspects. The dummy load on the 8920 RF port is OK, but I'd still be more comfortable using a good external load and isotee. Intermittant desense can sometimes be traced back to a component or solder joint in the transmitter being defective, which can manifest as arcing (however microscopic). The resulting transmitter noise may not be easily discernable on a spectrum analyzer, especially without attenuation of the carrier frequency to increase the dynamic range of the test equipment, but may still cause appreciable desense due to the broadband noise falling on the Rx frequency. Yes, half of the duplexer's job is to attenuate transmitter noise to keep it from getting to the receiver, but if a failing component causes the effective noise level to be elevated 20 or 30 dB, that's 20 or 30 dB more isolation your duplexer would need to provide to prevent desense, and often that kind of headroom doesn't exist. Have you measured the isolation of your duplexer from Tx port to Rx port with the antenna port terminated in a dummy load? What is the measured isolation at the Tx and Rx frequencies doing this test? --- Jeff WN3A
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
It's an analog supply built into the repeater. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Wednesday, October 08, 2008 11:55 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Just out of curiosity what power supply are you using? I've seen a fair amount of RFI from the Astron SS series. image001.jpgimage002.jpg
RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I thought that's what Skipp was saying but I wasn't sure. I think (without looking) the -8920 is good for 80dB. Gonna redo the duplex test with a different iso-tee, just on the off chance that something is amiss there. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Wednesday, October 08, 2008 1:03 PM To: Repeater-Builder@yahoogroups.com Subject: 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? Not to step on Skipp's toes, but I think what he was getting at is that spectrum analyzers have a limited dynamic range, probably around 80 dB. So you can only see noise/spurs down as low as 80 dB below carrier. If you crank up the gain (i.e. reduce the attenuation) on the spectrum analyzer higher, you will start to overload it with the carrier unless you have something (filter) to attenuate the transmitter carrier. It's quite easy to have low-level spurs and broadband noise that aren't immediately discernable on the spectrum analyzer, yet they're still strong enough to cause you problems at sub-microvolt receive levels. If I lower the power enough, the desense goes away. just as I'd expect. It's a matter of scale, after all. Does the desense taper off as you reduce power, or does it suddenly disappear at some power level? That can be a big clue. 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. That's good information. As I mentioned in a previous post, I'd suggest trying duplex desense tests with a good external load rather than the one built into the 8920 just to rule that out too. --- Jeff WN3A image001.jpgimage002.jpg
RE: [Repeater-Builder] Re: Desense with DB4060 Duplexer
Not so much one cavity more than the other... but on the TX side more than the other. Gonna try to play tonight. 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Wednesday, October 08, 2008 11:23 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Desense with DB4060 Duplexer On one specific cavity or more than one? You're almost at the problem. No garbage with tapping, beating and banging is a good sign. One might guess you have some type of micro pitting and at least one hard point pitted contact on one of the mating surfaces. One or more of the metal plunger contact surfaces has a not easily viewed problem. Just cleaning might not cure it sometimes you need to replace finger stock and or have at the surfaces with the proper cleaning brush/function. You didn't say how you'd cleaned the surface in the past. I would only use a Brass or hard Stainless Steel brush to avoid embedding non same metals into the plunger or contact surface. Using a common steel wire brush is not a good idea. s. Mike Besemer \(WM4B\) [EMAIL PROTECTED] wrote: Skipp, Doing that produces some interesting noises in the receiver. It will go from full-quieting to complete garbage without much movement. Tapping, beating, and banging seem to have little to no effect. I think I'm going to tear them down again and reclean all the mating surfaces. I MUST have missed something. 73, Mike
[Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Take a look here: http://www.repeater-builder.com/db/db-4060-4062-repair.pdf 73 Bernie K5BP --- In Repeater-Builder@yahoogroups.com, Ralph Hogan [EMAIL PROTECTED] wrote: While we are on the subject of the DB4060/62, I've got a couple of dead cans with a bad tuning cap. Does anyone have a source I can call to buy some of the Johanson 5602 tuning caps? Some of the Johanson distributors don't stock it and require a big min order. I've looked at Nebraska Surplus and they have some that might work, but I'd like to find the exact replacement if possible. Thanks, Ralph W4XE
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Tuesday, October 07, 2008 6:03 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, I can hear the fingerstock scraping against the inner tube... not a BAD scraping... just what sounds like good metal-to-metal contact. That is normal. The reason I asked is mine had stopped making that noise. It was almost completely silent when I rotated the knobs. That was one of the major things that led me to conclude something was really wrong inside. I knew silence when being tuned wasn't normal for those cans. After being refurbished it is back to making a healthy scraping sound. I was also thinking about cleaning the mating surfaces on the top... just need to get the gumption to do it. I'm getting tired of having my butt kicked! I know that feeling! I cleaned *every* mating surface while I had them apart, corrected some manufacturing sloppiness, and made a minor modification (which, I'm sure, was totally unnecessary, but I wasn't leaving any stone unturned). Good luck! 73, Paul N1BUG image001.jpgimage002.jpg
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes… looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white ‘stuff’ growing in there… have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed… a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is… which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Paul, I just noticed that what I wrote here was backwards... the 004s had the strap all the way around and the 005s had the wire extension. If I figure out what goes where, I'll let you know. Did you have trouble with the top of the inner loop catching on the fingerstock and tweaking it a bit? I bent a couple of mine, but it tweaked back into place okay. Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Forgot to mention... yes, the knobs were soldered on. I'm amazed they take that much heat without damage. I'm glad you figured that part out... it had me stumped. I'll report back with progress when I get them done. 73, Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
These babies are looking pretty rough, Paul (et al). After one pass with the synthetic steel wool and a wipe with isopropyl alcohol, I can see that the copper plating near the open end of the outer tubes is nearly gone on two of the cans. Have not done the other two yet, but they seem to be in better shape. I'm thinking more and more they're gonna need a refurb, although I can't see how they'd do anything with these, since the don't come apart any further. Anybody ever done a refurb from dbSpectra? Wish they'd return my calls/emails. Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
[Repeater-Builder] Re: Inquiry for vendor
---http://www.mapquest.com/maps?city=Greensborostate=NCaddress=%5B400- 499%5D+Scott+Avezipcode=27403country=USlatitude=36.06995longitude=- 79.83005geocode=STREET . . In Repeater-Builder@yahoogroups.com, Captainlance [EMAIL PROTECTED] wrote: Has anyone recently heard of or had contact with the following individual: Brian Shanks, 114 Scott Street, Goldsboro, NC operating as WWW.Surpluscoax.com if so, or if you are in the area and can verify the address, Please contact me. Captain Lance Alfieri NCAPD
[Repeater-Builder] Mitreks
How does one tell the differance between a High Low power and VHF or UHF Mitrek? Thankyou
RE: [Repeater-Builder] Mitreks
Randy, A low-power Mitrek chassis has fins that are about 1/2 deep, while the high-power units have fins that are about 1-1/2 deep. A VHF high-band radio (150-174 MHz) will have a 3 as the third character in the model number, as in T43JJA6900DK. A UHF radio will have a 4 in the same location. A low-band (30-50 MHz) Mitrek will have a 1 in that location. Be aware that some Mitrek models come in more than just two power levels. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Randy Sent: Wednesday, October 08, 2008 8:28 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Mitreks How does one tell the differance between a High Low power and VHF or UHF Mitrek? Thankyou
[Repeater-Builder] Linear uhf amp
Hi guys .Would anyone know where I can get a 100 watt uhf commercial amp 450-500mhz in Australia or us Thank You, Ian Wells, Kerinvale Comaudio, 361 Camboon Road.Biloela.4715 Phone 0749922574 or 0409159932 www.kerinvalecomaudio.com.au
