[Repeater-Builder] Re: Desense has me pulling my hair out!
I know from experience that aluminum oxide is a noise generator under RF conditions. - Or course, silver oxide is conductive, unlike most other oxides.
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.
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
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: 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
[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
[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
[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.
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
[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.
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
[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.
