Re: [Repeater-Builder] Re: New Repeater Desense Problems
I am wondering if a person could make an Iso Tee for a bird? I may have a slug that could be used as a basis for one, as I picked up several damaged slugs in an alley once. May have to possibly unbend one to get an okay fit, don't want to have to force one into my baby. Sometimes I wish that the dummy slug(s) that originallycame with mine had not been misplaced. My brother sold it to me a few years back, and the dummy slug(s) were not in with it. Mine never got abused, as I bought it new for my brothers shop. Anyway, an Iso Tee might be a good addition once I get a shop fixed up. And hoping I never come up with a desense problem when I set up a secondart repeater here. Wayne WA2YNE On Tue, 08 Jul 2008 22:47:18 -0500, de W5DK [EMAIL PROTECTED] wrote: I think he was Laryn. I could see an argument that it may not have been aligned and caused the situation. But,, In this case the matching circuit was installed and set properly, also the duplexers and all were perfect. The system was stable for years then boom, desense. All I was saying was that this station worked Perfect into a dummy load (zero desense and all to spec) but did not into feedline(+15db) . So we cringed and focused there. We were getting ready to replace the antenna at 580 ft and spend some money after the dummy load test. Luckily the amp finished failing. What I relayed locally after this experience was that a complete system that works flawlessly into a dummy load may not be flawless. I do think the majority of desense problems can be diagnosed with a dummy load and a sampler slug / iso tee. I just wanted to throw a recent experience / monkey wrench into the thread hi. 73 Don W5DK -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/ 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] Re: New Repeater Desense Problems
See http://www.repeater-builder.com/projects/bird43sampler.html and from WA1MIK a writeup on what is inside a Bird element, as he fixed it... http://www.repeater-builder.com/projects/bird-element-tour/bird-element-tour.html Mike WA6ILQ At 01:41 PM 07/19/08, you wrote: I am wondering if a person could make an Iso Tee for a bird? I may have a slug that could be used as a basis for one, as I picked up several damaged slugs in an alley once. May have to possibly unbend one to get an okay fit, don't want to have to force one into my baby. Sometimes I wish that the dummy slug(s) that originallycame with mine had not been misplaced. My brother sold it to me a few years back, and the dummy slug(s) were not in with it. Mine never got abused, as I bought it new for my brothers shop. Anyway, an Iso Tee might be a good addition once I get a shop fixed up. And hoping I never come up with a desense problem when I set up a secondart repeater here. Wayne WA2YNE On Tue, 08 Jul 2008 22:47:18 -0500, de W5DK [EMAIL PROTECTED] wrote: I think he was Laryn. I could see an argument that it may not have been aligned and caused the situation. But,, In this case the matching circuit was installed and set properly, also the duplexers and all were perfect. The system was stable for years then boom, desense. All I was saying was that this station worked Perfect into a dummy load (zero desense and all to spec) but did not into feedline(+15db) . So we cringed and focused there. We were getting ready to replace the antenna at 580 ft and spend some money after the dummy load test. Luckily the amp finished failing. What I relayed locally after this experience was that a complete system that works flawlessly into a dummy load may not be flawless. I do think the majority of desense problems can be diagnosed with a dummy load and a sampler slug / iso tee. I just wanted to throw a recent experience / monkey wrench into the thread hi. 73 Don W5DK -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/ Yahoo! Groups Links
Re: [Repeater-Builder] Re: New Repeater Desense Problems
Build a simple RF sampler for the Bird Model 43 Thruline Wattmeter By Kevin K. Custer W3KKC http://www.repeater-builder.com/projects/bird43sampler.html - Original Message - From: Wayne [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Saturday, July 19, 2008 4:41 PM Subject: Re: [Repeater-Builder] Re: New Repeater Desense Problems I am wondering if a person could make an Iso Tee for a bird? I may have a slug that could be used as a basis for one, as I picked up several damaged slugs in an alley once. May have to possibly unbend one to get an okay fit, don't want to have to force one into my baby. Sometimes I wish that the dummy slug(s) that originallycame with mine had not been misplaced. My brother sold it to me a few years back, and the dummy slug(s) were not in with it. Mine never got abused, as I bought it new for my brothers shop. Anyway, an Iso Tee might be a good addition once I get a shop fixed up. And hoping I never come up with a desense problem when I set up a secondart repeater here. Wayne WA2YNE On Tue, 08 Jul 2008 22:47:18 -0500, de W5DK [EMAIL PROTECTED] wrote: I think he was Laryn. I could see an argument that it may not have been aligned and caused the situation. But,, In this case the matching circuit was installed and set properly, also the duplexers and all were perfect. The system was stable for years then boom, desense. All I was saying was that this station worked Perfect into a dummy load (zero desense and all to spec) but did not into feedline(+15db) . So we cringed and focused there. We were getting ready to replace the antenna at 580 ft and spend some money after the dummy load test. Luckily the amp finished failing. What I relayed locally after this experience was that a complete system that works flawlessly into a dummy load may not be flawless. I do think the majority of desense problems can be diagnosed with a dummy load and a sampler slug / iso tee. I just wanted to throw a recent experience / monkey wrench into the thread hi. 73 Don W5DK -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/ Yahoo! Groups Links 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] Re: New Repeater Desense Problems
Laryn Lohman wrote: A Z matcher's purpose is basically to maximize the efficiency of the amplifier. So with our repeater transmitter (VHF), which is two amps rated at 225 watts when combined, I adjusted them for minimum current draw at max power out. As you adjust, you'll soon find combinations that substantially reduce the current draw with no loss in power out. I like this idea. Might as well try it. :-) I've also added fans to the heatsinks and to the component side of all (3) amps in this transmitter. Power out is set to 180 watts and so far, zero trouble in 7 years. I admit that my experience with these amps is much more limited than yours, Nate, so my luck may catch up some day. I want to add fans too. I know the things are EIA rated for 100% continuous-duty, but the number one killer of RF power transistors is internal metal migration due to heat... so shedding heat in any way possible seems like a good idea. Interestingly, most PA's are also only rated for continuous-duty at full power output up to 10,000' MSL. With one site here at 9,000' MSL and the other at 11,440' MSL and two others around 8500' MSL, I figure they're all running in the harder to cool end of the specification band. All above 85% of the rated altitude numbers. So cooling has been a worry for a while, but I haven't fashioned something I like for mounting fans on them. I've seen a number of used MASTR II PA's with fans tie-wrapped to the front cover... that would certainly help too, I suppose. Even Crescend only specs up to 10,000' MSL, and their commercial stuff (while pricey) is well-respected here in the list and off. Then add our insidious lightning, and I'm sure they're being abused... to some extent. But frankly, even if I have more experience than you do, all I've been accomplishing is blowing them up -- ha! -- so I might as well try other ideas! (To be honest, out of frustration a couple of our techs pointed out that one of our systems ran for close to ten years on a Henry PA, and that the PA was still in the club's storage -- otherwise known as my basement. I called Henry and they offered to modify it for a 1/4W input and re-tune it to the problematic site's frequency critically on their bench for less than $100... so off it went. It's back from Henry and sitting here tempting me to go put it in and see what it can do. The physical mounting is a problem at that site, so I don't know if it's worth trying or not. Out of curiosity, anyone reading along running any Henry PA's on their systems, or have any thoughts on the idea?) Nate WY0X
Re: [Repeater-Builder] Re: New Repeater Desense Problems
Laryn Lohman wrote: --- In Repeater-Builder@yahoogroups.com, wd8chl [EMAIL PROTECTED] wrote: It sounds to me like the PA wasn't aligned properly. Or the duplexer is not aligned properly. Most, but not all, MastrII PA's have an output filter section that is tricky to align correctly. Are you referring to the Z matching adjustments on continuous-duty amps? Laryn K8TVZ Yeah.
RE: [Repeater-Builder] Re: New Repeater Desense Problems
So, please, someone tell me, what is an iso tee/sampler slug? How is the equipment hooked up for the desense test? John -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of de W5DK Sent: Tuesday, July 08, 2008 11:47 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: New Repeater Desense Problems I think he was Laryn. I could see an argument that it may not have been aligned and caused the situation. But,, In this case the matching circuit was installed and set properly, also the duplexers and all were perfect. The system was stable for years then boom, desense. All I was saying was that this station worked Perfect into a dummy load (zero desense and all to spec) but did not into feedline(+15db) . So we cringed and focused there. We were getting ready to replace the antenna at 580 ft and spend some money after the dummy load test. Luckily the amp finished failing. What I relayed locally after this experience was that a complete system that works flawlessly into a dummy load may not be flawless. I do think the majority of desense problems can be diagnosed with a dummy load and a sampler slug / iso tee. I just wanted to throw a recent experience / monkey wrench into the thread hi. 73 Don W5DK m: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Laryn Lohman Sent: Tuesday, July 08, 2008 8:50 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: New Repeater Desense Problems --- In Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com, wd8chl [EMAIL PROTECTED] wrote: It sounds to me like the PA wasn't aligned properly. Or the duplexer is not aligned properly. Most, but not all, MastrII PA's have an output filter section that is tricky to align correctly. Are you referring to the Z matching adjustments on continuous-duty amps? Laryn K8TVZ __ NOD32 3192 (20080616) Information __ This message was checked by NOD32 antivirus system. http://www.eset.com
Re: RE: [Repeater-Builder] Re: New Repeater Desense Problems
John, The tee/sampler slug is simply a loosely coupled connection to the coax so one can insert say a generator signal into the coax without dumping the power of the transmitter back into the signal gen. One way to build one is to take a coaxial T connector, remove the center pin of the vertical part (it often unscrews) of the T essentally making it a barral connector with the vertical part of the T open except for a few pf of capacitance between the center of the line and the vertical T output. One can then connect a signal gen to the vertical part of the T while it is in the regualar coax line with power from the tx on/keyed. To do a desense test insert the barral in the antenna line with sig gen connected to the vertical part of the T. First with TX UNKEYED cranks up the sig gen to get a low level say 12 db quieting with some noise at the receiver. This level will be much higher than if connected directly to the receiver. Then key the transmitter and see what happens to the receiver. It will probably show some desense, but very little in a good system. If a lot then crank up the sig gen to get the same rcvr quieting level as without the TX and this tells you how much desense you have. It is the same as having a weak DX station transmit to the repeater with the TX keyed and unkeyed. However, with the sig gen you can get more of an idea of any problem. Also this can be done with a dummy load in the event you suspect an antenna/feedline problem. Any repeater will not only have desense or noise from the tepater transmitter. It will have noise from outside sources so using this with the antenna connected can tell you the system noise. I did not invent it...it was around I am sure decades ago and there are professional built units on the market. A modified T connector is just an inexpensive way to get one. 73, ron, n9ee/r From: John Transue [EMAIL PROTECTED] Date: 2008/07/09 Wed AM 10:06:35 EDT To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: New Repeater Desense Problems So,please, someone tell me, what is an iso tee/sampler slug? How is the equipmenthooked up for the desense test? John -Original Message- From:Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of de W5DK Sent: Tuesday, July 08, 2008 11:47PM To:Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder]Re: New Repeater Desense Problems I think he was Laryn. I could see anargument that it may not have been aligned and caused the situation. But,, In this case the matching circuitwas installed and set properly, also the duplexers and all were perfect. Thesystem was stable for years then boom, desense. All I was saying was that this stationworked Perfect into a dummy load (zero desense and all to spec) but did notinto feedline(+15db) . So we cringed and focused there. We were getting ready to replace theantenna at 580 ft and spend some money after the dummy load test. Luckily theamp finished failing. What I relayed locally after this experience was that acomplete system that works flawlessly into a dummy load may not be flawless. I do think the majority of desense problemscan be diagnosed with a dummy load and a sampler slug / iso tee. I just wantedto throw a recent experience / monkey wrench into the thread hi. 73 Don W5DK m: [EMAIL PROTECTED]:[EMAIL PROTECTED] On Behalf Of Laryn Lohman Sent: Tuesday, July 08, 2008 8:50PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re:New Repeater Desense Problems --- In Repeater-Builder@yahoogroups.com,wd8chl [EMAIL PROTECTED] wrote: It sounds to me like the PA wasn't aligned properly. Or the duplexer is not aligned properly. Most, but not all, MastrII PA's have an output filter section that is tricky to align correctly. Are you referring to the Z matching adjustments on continuous-duty amps? Laryn K8TVZ __ NOD32 3192 (20080616) Information __ This message was checked by NOD32 antivirus system. http://www.eset.com Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: [Repeater-Builder] Re: New Repeater Desense Problems
Using a Mike quote doesn't anybody read the site?!!! http://www.repeater-builder.com/projects/bird43sampler.html sorry John could resist J and Ron's description / answer was correct. 73 Don W5DK From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of John Transue Sent: Wednesday, July 09, 2008 9:07 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: New Repeater Desense Problems So, please, someone tell me, what is an iso tee/sampler slug? How is the equipment hooked up for the desense test? John -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of de W5DK Sent: Tuesday, July 08, 2008 11:47 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: New Repeater Desense Problems I think he was Laryn. I could see an argument that it may not have been aligned and caused the situation. But,, In this case the matching circuit was installed and set properly, also the duplexers and all were perfect. The system was stable for years then boom, desense. All I was saying was that this station worked Perfect into a dummy load (zero desense and all to spec) but did not into feedline(+15db) . So we cringed and focused there. We were getting ready to replace the antenna at 580 ft and spend some money after the dummy load test. Luckily the amp finished failing. What I relayed locally after this experience was that a complete system that works flawlessly into a dummy load may not be flawless. I do think the majority of desense problems can be diagnosed with a dummy load and a sampler slug / iso tee. I just wanted to throw a recent experience / monkey wrench into the thread hi. 73 Don W5DK m: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Laryn Lohman Sent: Tuesday, July 08, 2008 8:50 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: New Repeater Desense Problems --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com , wd8chl [EMAIL PROTECTED] wrote: It sounds to me like the PA wasn't aligned properly. Or the duplexer is not aligned properly. Most, but not all, MastrII PA's have an output filter section that is tricky to align correctly. Are you referring to the Z matching adjustments on continuous-duty amps? Laryn K8TVZ __ NOD32 3192 (20080616) Information __ This message was checked by NOD32 antivirus system. http://www.eset.com
RE: [Repeater-Builder] Re: New Repeater Desense Problems
Don, that only works if he owns a Bird 43 or similar meter. ;-) He can also construct one of his own from a UHF T connector. Now, a question of my own. Kevin (or anyone else) will this also work with a Bird 4410 (multi-range) meter?? If so, I'll build one at my next convenience! Mark - N9WYS From: Repeater-Builder@yahoogroups.com On Behalf Of de W5DK Using a Mike quote doesn't anybody read the site?!!! http://www.repeater-builder.com/projects/bird43sampler.html sorry John could resist J and Ron's description / answer was correct. 73 Don W5DK From: Repeater-Builder@yahoogroups.com On Behalf Of John Transue So, please, someone tell me, what is an iso tee/sampler slug? How is the equipment hooked up for the desense test? John
RE: [Repeater-Builder] Re: New Repeater Desense Problems
From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Nate Duehr On Jul 8, 2008, at 9:47 PM, de W5DK wrote: We were getting ready to replace the antenna at 580 ft and spend some money after the dummy load test. Luckily the amp finished failing. What I relayed locally after this experience was that a complete system that works flawlessly into a dummy load may not be flawless. Don, I think you said you looked at the PA output with a spectrum analyzer prior to its failure -- did you see anything? Was your MASTR II VHF, or UHF? Nate Ours was VHF. I did look at it with my HP8921 SA, into a dummy, into the antenna, varied the output. Over the air and through the sampler. Rechecked the matching, bypass the isolator. I really wanted to find a problem at the ground level. The dynamic range of the SA will only let you see so low. BTW, I only had a 30 minute driveJ Parts are getting harder to find. So who has the all inclusive instructions and part numbers to install an RF brick into a master II station VHF and UHF versions of course. J 73 Don
RE: RE: [Repeater-Builder] Re: New Repeater Desense Problems
Ron N9EE Don W5DK Mark N9WYS Thanks to all who replied. This is a big help. As it turns out, I have a Bird meter with a model 4275-100 port. I believe this will act as an iso tee. Am I right in believing this is the Bird way to provide for injection or sampling? John -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Wednesday, July 09, 2008 10:31 AM To: Repeater-Builder@yahoogroups.com Subject: Re: RE: [Repeater-Builder] Re: New Repeater Desense Problems John, The tee/sampler slug is simply a loosely coupled connection to the coax so one can insert say a generator signal into the coax without dumping the power of the transmitter back into the signal gen. One way to build one is to take a coaxial T connector, remove the center pin of the vertical part (it often unscrews) of the T essentally making it a barral connector with the vertical part of the T open except for a few pf of capacitance between the center of the line and the vertical T output. One can then connect a signal gen to the vertical part of the T while it is in the regualar coax line with power from the tx on/keyed. To do a desense test insert the barral in the antenna line with sig gen connected to the vertical part of the T. First with TX UNKEYED cranks up the sig gen to get a low level say 12 db quieting with some noise at the receiver. This level will be much higher than if connected directly to the receiver. Then key the transmitter and see what happens to the receiver. It will probably show some desense, but very little in a good system. If a lot then crank up the sig gen to get the same rcvr quieting level as without the TX and this tells you how much desense you have. It is the same as having a weak DX station transmit to the repeater with the TX keyed and unkeyed. However, with the sig gen you can get more of an idea of any problem. Also this can be done with a dummy load in the event you suspect an antenna/feedline problem. Any repeater will not only have desense or noise from the tepater transmitter. It will have noise from outside sources so using this with the antenna connected can tell you the system noise. I did not invent it...it was around I am sure decades ago and there are professional built units on the market. A modified T connector is just an inexpensive way to get one. 73, ron, n9ee/r From: John Transue [EMAIL PROTECTED] mailto:jtransue%40cox.net net Date: 2008/07/09 Wed AM 10:06:35 EDT To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: RE: [Repeater-Builder] Re: New Repeater Desense Problems So,please, someone tell me, what is an iso tee/sampler slug? How is the equipmenthooked up for the desense test? John -Original Message- From:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com [mailto:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com] On Behalf Of de W5DK Sent: Tuesday, July 08, 2008 11:47PM To:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: RE: [Repeater-Builder]Re: New Repeater Desense Problems I think he was Laryn. I could see anargument that it may not have been aligned and caused the situation. But,, In this case the matching circuitwas installed and set properly, also the duplexers and all were perfect. Thesystem was stable for years then boom, desense. All I was saying was that this stationworked Perfect into a dummy load (zero desense and all to spec) but did notinto feedline(+15db) . So we cringed and focused there. We were getting ready to replace theantenna at 580 ft and spend some money after the dummy load test. Luckily theamp finished failing. What I relayed locally after this experience was that acomplete system that works flawlessly into a dummy load may not be flawless. I do think the majority of desense problemscan be diagnosed with a dummy load and a sampler slug / iso tee. I just wantedto throw a recent experience / monkey wrench into the thread hi. 73 Don W5DK m: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com[mailto:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com] On Behalf Of Laryn Lohman Sent: Tuesday, July 08, 2008 8:50PM To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: [Repeater-Builder] Re:New Repeater Desense Problems --- In Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com,wd8chl [EMAIL PROTECTED] wrote: It sounds to me like the PA wasn't aligned properly. Or the duplexer is not aligned properly. Most, but not all, MastrII PA's have an output filter section that is tricky to align correctly. Are you referring to the Z matching adjustments on continuous-duty amps? Laryn K8TVZ __ NOD32 3192 (20080616) Information __ This message was checked by NOD32 antivirus system. http://www.eset
Re: [Repeater-Builder] Re: New Repeater Desense Problems
wd8chl wrote: Laryn Lohman wrote: --- In Repeater-Builder@yahoogroups.com, wd8chl [EMAIL PROTECTED] wrote: It sounds to me like the PA wasn't aligned properly. Or the duplexer is not aligned properly. Most, but not all, MastrII PA's have an output filter section that is tricky to align correctly. Are you referring to the Z matching adjustments on continuous-duty amps? Laryn K8TVZ Yeah. I wouldn't call GE's instructions on how to align them tricky at all. But there's been debates here in the past as to whether or not GE's instructions would REALLY be setting the correct match (since you're just tuning for a voltage at a test point). Nate WY0X
RE: [Repeater-Builder] Re: New Repeater Desense Problems
I think he was Laryn. I could see an argument that it may not have been aligned and caused the situation. But,, In this case the matching circuit was installed and set properly, also the duplexers and all were perfect. The system was stable for years then boom, desense. All I was saying was that this station worked Perfect into a dummy load (zero desense and all to spec) but did not into feedline(+15db) . So we cringed and focused there. We were getting ready to replace the antenna at 580 ft and spend some money after the dummy load test. Luckily the amp finished failing. What I relayed locally after this experience was that a complete system that works flawlessly into a dummy load may not be flawless. I do think the majority of desense problems can be diagnosed with a dummy load and a sampler slug / iso tee. I just wanted to throw a recent experience / monkey wrench into the thread hi. 73 Don W5DK m: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Laryn Lohman Sent: Tuesday, July 08, 2008 8:50 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: New Repeater Desense Problems --- In Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com , wd8chl [EMAIL PROTECTED] wrote: It sounds to me like the PA wasn't aligned properly. Or the duplexer is not aligned properly. Most, but not all, MastrII PA's have an output filter section that is tricky to align correctly. Are you referring to the Z matching adjustments on continuous-duty amps? Laryn K8TVZ
Re: [Repeater-Builder] Re: New Repeater Desense Problems
On Jul 8, 2008, at 9:47 PM, de W5DK wrote: We were getting ready to replace the antenna at 580 ft and spend some money after the dummy load test. Luckily the amp finished failing. What I relayed locally after this experience was that a complete system that works flawlessly into a dummy load may not be flawless. Don, I think you said you looked at the PA output with a spectrum analyzer prior to its failure -- did you see anything? Was your MASTR II VHF, or UHF? Just curious. I've been fighting VHF MASTR II PA's for years here... I've got (literally) a pile of the continuous-duty PA's that need some sort of repair or another. UHF on the other hand, just work forever. It's a heartbreaker to have watched a friend meticulously rebuild a MASTR II VHF PA including following all the manufacturer specified torques for every single screw, including replacing all the thermal grease correctly with new after cleaning the thing up, using the right solder and heat to put everything back together with the newest mobile components we could find, hooking it to a WELL tested (we were already well into the troubleshooting stage/question of Why do these things blow up, damn-it!?) commercial antenna fed with good hardline, an isolator, swept with a Sitemaster... yadda, yadda, yadda Only to see that one die in 6 months time. Enough to REALLY piss you off -- when your mentors tell you that there must still be something wrong with the antenna system. Yeah, whatever... at 125 miles round trip to that site, I'm not sure I care anymore at today's gas prices. Tired of replacing the dang things. I think SOME of these in this pile are just old and were abused (overheated) in their lifetimes, but others... like this complete rebuild, were flawless. Then *pop*. Dead. Gr. -- Nate Duehr, WY0X [EMAIL PROTECTED]
