Re: [Repeater-Builder] ENHANCED RECEIVE
At 07:47 PM 08/18/09, you wrote: I have heard of repeater owners using pre-amps on the receive side of the duplexer and adding 1 pass-reject cavity after the preamp and placing a pre-amp on the pass reject cavity to enhance more receive. Does this work or is it a myth? Artie k2aau Depends on if you have enough headroom in the duplexer and enough system isolation. http://www.repeater-builder.com/rbtip/preamps.html While this is on 900MHz the theory and comments are just as applicable on 2m, 220 and 440. http://www.repeater-builder.com/tech-info/speaking-of-preamps.html
Re: [Repeater-Builder] ENHANCED RECEIVE
Mike, Pre-amps are fine if you need to reduce feedline and connector loss, for those lucky few that have antennas way up on commercial towers and have significant loss. Otherwise, nada. Signal to noise is not improved and can be effected negatively. Pre-amps can also be easily overloaded by pager and other nearby signals. Lastly, the pre-amps are physically sensitive devices when it comes to EMP...IMHO. If you want to improved receive capture area or coverage think satellite receivers. 73, dave wa3gin - Original Message - From: Mike Morris WA6ILQ To: Repeater-Builder@yahoogroups.com Sent: Wednesday, August 19, 2009 4:43 AM Subject: Re: [Repeater-Builder] ENHANCED RECEIVE At 07:47 PM 08/18/09, you wrote: I have heard of repeater owners using pre-amps on the receive side of the duplexer and adding 1 pass-reject cavity after the preamp and placing a pre-amp on the pass reject cavity to enhance more receive. Does this work or is it a myth? Artie k2aau Depends on if you have enough headroom in the duplexer and enough system isolation. http://www.repeater-builder.com/rbtip/preamps.html While this is on 900MHz the theory and comments are just as applicable on 2m, 220 and 440. http://www.repeater-builder.com/tech-info/speaking-of-preamps.html
Re: [Repeater-Builder] Antenna Type?
GM Lee - Tks for input. I don't have an analyzer here. Best I can do is an old military AN/PRM-10 GDO. I think (since I never venture up into that region) it goes up to a couple hundred mhz so will eventually try that. I'm primarily interested in moving all this estate stuff out of my garage at the moment. Its so packed out there with it (and my own gear) you can't blow smoke in there. Man, I'll never get involved with an estate again, at least not thats 100% stuff I don't understand (maybe would do it with vintage tube HF stuff, etc). That pix on the website was a dead ringer for what we have here. Only difference was the overall length (I had 7'2 and their catalog had 8') but then I realized, I measured to the end of the element (the black rod) only and the catalog probably measured the overall lenght (including the base) which I didn't. Now we're both at 8'. Anyway, again, tks for the invaluable help. 73 Walt (N4GL) --- On Tue, 8/18/09, Lee Pennington localjunkpedd...@gmail.com wrote: From: Lee Pennington localjunkpedd...@gmail.com Subject: Re: [Repeater-Builder] Antenna Type? To: Repeater-Builder@yahoogroups.com Date: Tuesday, August 18, 2009, 3:29 PM Exactly right, and since they were black in color, I would guess they were older antennas from Comet . But thats only a guess. If you have an antenna analyzer check and see what the resonant frequency is. de Lee K4LJP 73 On Tue, Aug 18, 2009 at 2:58 PM, Walter Treftz sjotrol...@yahoo. com wrote: GA Lee - mni tks for the response. repeater pair -- do you mean, perhaps, one was used for rcvr and one for xmtr? The SK had his own 220 repeater for use of just him and his XYL so it could well be possible. Any idea on the mfr or model? With that maybe I could find something online. Would a pix help you ID it? If so, I can take some and send them to you. 73 Walt (N4GL) --- On Tue, 8/18/09, Lee Pennington localjunkpeddler@ gmail.com wrote: From: Lee Pennington localjunkpeddler@ gmail.com Subject: Re: [Repeater-Builder] Antenna Type? To: Repeater-Builder@ yahoogroups. com Date: Tuesday, August 18, 2009, 10:42 AM 12 inch radials??, Sounds like a 222 repeater pair (no duplexer) of antennas. de Lee K4LJP 73 On Tue, Aug 18, 2009 at 8:52 AM, sjotrollet sjotrol...@yahoo. com wrote: As part of an estate we're assisting with, would anyone know the type, mfr, freq band. etc (or any info at all) on the following ant? There are two of them here, one is new. The SK was DEEP into VHF/UHF (having his own 2m 220 repeaters) so feel they are maybe 2m or 220 mhz. Anyway, any help would be appreciated. There are no numbers or mfr names on either. Both are identical. Black plastic construction 7 ft 2 in +/- long 1 dia at bottom of the element, 3/4 at the top. Single vertical member UHF coax connector on the bottom 3 ea 12 horizontal ground plane elements at the bottom. 73 Walt (N4GL) -- Always drink upstream from the herd. -- Always drink upstream from the herd.
Re: [Repeater-Builder] ENHANCED RECEIVE
This particular commentary seems somewhat inaccurate in saying signal to noise cannot be improved...as even GE offered a factory preamp for the Mastr II in VHF and UHF. The sensitivity spec improvedThey DID NOT suggest using it in a station environment as THEIR preamp overloads very easily in Site conditions As it bolted into the front housing ( just inside the antenna jack) of the receiver, it sure was not offered to correct cable loss. :-) .. This would seem to suggest that a preamp can, and will help ... but as it is subjected to site issues, it needs to be appropriately designed. This is mentioned repeatedly in the hyperlinked documents and various other sites. The noise figure of a stock Mastr II receiving system can definitely be improved upon with a preamp, as can other receivers designed in that time period if done correctly ! Many modern LMR type receivers may NOT improve much, especially if they already have sub .2uv sensitivity to start with. In that case a preamp would likely cause more harm than good unless tower mounted at the antenna (and in that case would be to overcome losses in the feedline as noted below by Dave). Doug KD8B At 07:39 AM 8/19/2009, you wrote: Mike, Pre-amps are fine if you need to reduce feedline and connector loss, for those lucky few that have antennas way up on commercial towers and have significant loss. Otherwise, nada. Signal to noise is not improved and can be effected negatively. Pre-amps can also be easily overloaded by pager and other nearby signals. Lastly, the pre-amps are physically sensitive devices when it comes to EMP...IMHO. If you want to improved receive capture area or coverage think satellite receivers. 73, dave wa3gin - Original Message - From: mailto:wa6...@gmail.comMike Morris WA6ILQ To: mailto:Repeater-Builder@yahoogroups.comRepeater-Builder@yahoogroups.com Sent: Wednesday, August 19, 2009 4:43 AM Subject: Re: [Repeater-Builder] ENHANCED RECEIVE At 07:47 PM 08/18/09, you wrote: I have heard of repeater owners using pre-amps on the receive side of the duplexer and adding 1 pass-reject cavity after the preamp and placing a pre-amp on the pass reject cavity to enhance more receive. Does this work or is it a myth? Artie k2aau Depends on if you have enough headroom in the duplexer and enough system isolation. http://www.repeater-builder.com/rbtip/preamps.htmlhttp://www.repeater-builder.com/rbtip/preamps.html While this is on 900MHz the theory and comments are just as applicable on 2m, 220 and 440. http://www.repeater-builder.com/tech-info/speaking-of-preamps.htmlhttp://www.repeater-builder.com/tech-info/speaking-of-preamps.html
[Repeater-Builder] DB-224 Matching
In my quest to get rid of desense with the Quantar, someone mentioned that having the 'wrong' antenna could make the desense worse. I've got a DB-224 - not the 'ham' version, but the 150-160 MHz version, and there is a bit of a mismatch. Has anyone ever had any desense that they could attribute to less than perfect matching? (I'm not talking about a gross problem, like one of the elements broken, etc) Has anyone built a 'tuner' for that version of the 224, so that the transmitter/duplexer pair would see a better SWR? If this thing ever gets up, it's gonna be perfect! :-) Thanks, Tim W5FN
[Repeater-Builder] Re: ENHANCED RECEIVE
Most of the replies so far indicate a failure to read the original post *SLOWLY*. TWO preamps, one after the duplexer and then another one after a pass-reject cavity. This sounds wrong to me under any circumstances. The pass-reject cavity should have at most 1 or 2 db of loss, adding yet another preamp to the chain is going to do nothing other than decrease intermod performance. If it were me I'd lose the preamp between the duplexer and the cavity and keep the one between the cavity and receiver. Additionally unless I was trying to reject a specific signal other than my repeater's transmitter I'd use a plain pass cavity rather than a pass-reject to get better selectivity. If a pass-reject is needed for the repeater's transmitter you really need to upgrade the duplexer. 73's Skip WB6YMH --- In Repeater-Builder@yahoogroups.com, k2aau k2...@... wrote: I have heard of repeater owners using pre-amps on the receive side of the duplexer and adding 1 pass-reject cavity after the preamp and placing a pre-amp on the pass reject cavity to enhance more receive. Does this work or is it a myth? Artie k2aau
Re: [Repeater-Builder] ENHANCED RECEIVE
k2aau wrote: I have heard of repeater owners using pre-amps on the receive side of the duplexer and adding 1 pass-reject cavity after the preamp and placing a pre-amp on the pass reject cavity to enhance more receive. Does this work or is it a myth? It does work on UHF. I have no experience on VHF because the quality of the preamp needed has always been out of my budget, but I believe it could work here as well. Basically, you separate the duplexer receive path between the first and subsequent stages, place a quality preamp between these sections. Then take the output of the receive path of the duplexer arrangement and feed a bandpass cavity - that output feeds a second preamp; which feeds the repeater receiver. I have used this theory on Motorola MICOR repeaters with a common 4 cavity WACOM UHF duplexer. It should only be considered if you have an extremely clean site and quiet nearby RF environment. You need to insure the interstage preamp is not driven into non linear operation, especially when the transmitter is on (sigh). Chip Angle manufactures preamps with a very high overload point - well suited for this type of experiment. Basically you are taking advantage of minimizing the losses ahead of the first preamp while insuring you aren't blowing it away. Then using a subsequent preamp (really as a post amp) to finish adding gain to make up for any additional losses. Obviously we can't put a preamp in the antenna line of a duplex repeater using one feedline, but, getting the preamp as close to the antenna as possible (without destroying it) allows us to take advantage of better S/N ration to the first active device - making the system noise figure better. Kevin Custer
Re: [Repeater-Builder] DB-224 Matching
What frequency pair in 2m do you have? Have you thought about putting ss bollts through the bottoms and tops of the loops to bring the db-224a down in frequency? 73 de N5NPO Norm - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Wed Aug 19 08:40:31 2009 Subject: [Repeater-Builder] DB-224 Matching In my quest to get rid of desense with the Quantar, someone mentioned that having the 'wrong' antenna could make the desense worse. I've got a DB-224 - not the 'ham' version, but the 150-160 MHz version, and there is a bit of a mismatch. Has anyone ever had any desense that they could attribute to less than perfect matching? (I'm not talking about a gross problem, like one of the elements broken, etc) Has anyone built a 'tuner' for that version of the 224, so that the transmitter/duplexer pair would see a better SWR? If this thing ever gets up, it's gonna be perfect! :-) Thanks, Tim W5FN
[Repeater-Builder] Re: DB-224 Matching
Hi Norm, It's 147.10/70, so at least it's up high in the band. I thought about adding some metal to the loops, but figured I'd ask around here to see if it's been done before. Thanks, Tim --- In Repeater-Builder@yahoogroups.com, NORM KNAPP nkn...@... wrote: What frequency pair in 2m do you have? Have you thought about putting ss bollts through the bottoms and tops of the loops to bring the db-224a down in frequency? 73 de N5NPO Norm - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Wed Aug 19 08:40:31 2009 Subject: [Repeater-Builder] DB-224 Matching In my quest to get rid of desense with the Quantar, someone mentioned that having the 'wrong' antenna could make the desense worse. I've got a DB-224 - not the 'ham' version, but the 150-160 MHz version, and there is a bit of a mismatch. Has anyone ever had any desense that they could attribute to less than perfect matching? (I'm not talking about a gross problem, like one of the elements broken, etc) Has anyone built a 'tuner' for that version of the 224, so that the transmitter/duplexer pair would see a better SWR? If this thing ever gets up, it's gonna be perfect! :-) Thanks, Tim W5FN
[Repeater-Builder] COR board for simple repeater??
Hi all i am looking a COR board that i could use between 2 walkie-talkie that would be used here as a replacement for my regular repeater in case of accident. i have seen this many years ago,an amateur built his own repeater with 2 talkie's,simple and efficient. So maybe someone know where i could find such a board,,,controler what ever you call it,no need for queue,,,just a simple repeater. thanks Gervais ve2ckn
Re: [Repeater-Builder] COR board for simple repeater??
hi Gervais I have such a item .. its an alinco controller it was ment to have 2 HTs on it .. or even one and then act as a 'parrot' repeater if you would like more info email me off list On Wed, Aug 19, 2009 at 5:19 PM, gervaisve2...@hotmail.com wrote: Hi all i am looking a COR board that i could use between 2 walkie-talkie that would be used here as a replacement for my regular repeater in case of accident. i have seen this many years ago,an amateur built his own repeater with 2 talkie's,simple and efficient. So maybe someone know where i could find such a board,,,controler what ever you call it,no need for queue,,,just a simple repeater. thanks Gervais ve2ckn
Re: [Repeater-Builder] DB-224 Matching
Have you checked the repeater for desense without the antenna installed? As in most commercial repeaters they are usually designed for larger spacing than 600 kHz. Check it without the antenna and all open ports terminated with a 50 ohm termination. Then add the antenna and look at the difference. I have had problems where I had to split the transmit and receive to two different antennas and split the duplexers accordingly. I also chased this down once to a cheap right angle connector, the manufacturer used a spring to make the turn and it made a neat detector!..Jim
Re: [Repeater-Builder] COR board for simple repeater??
MFJ make one, check their catalog...
[Repeater-Builder] Re: COR board for simple repeater??
Depends on a few things... do you want the repeater to key on received voice/speaker volume level detection or from a logic level change like a carrier squelch or CTCSS (PL) detection logic? Voice audio detection can work OK if you consider the key up delay in the repeat path, but using two voice triggered circuits each direction for a bi-directional repeater doesn't work so well. s. gervais ve2...@... wrote: Hi all i am looking a COR board that i could use between 2 walkie-talkie that would be used here as a replacement for my regular repeater in case of accident. i have seen this many years ago,an amateur built his own repeater with 2 talkie's,simple and efficient. So maybe someone know where i could find such a board,,,controler what ever you call it,no need for queue,,,just a simple repeater. thanks Gervais ve2ckn
[Repeater-Builder] Need a TLD-2601A PA
Our club's MSR-2000 repeater recently ate it's PA, a TLD-2601A. Actually it went intermittent on us and several folks have gone over it with the magnifying glass and reflowed most of the major solder joints to no avail. That's a low split, 100 watt, continuous duty PA. If anyone has one available we are interested. We are in the Baltimore Washington area and could pick up within a reasonable distance (whatever the heck that is!) rather than shipping the fairly heavy unit. 73 de Tom/W4OKW (K3HKI Rpt)
Re: [Repeater-Builder] Need a TLD-2601A PA
Desolder the flat gold plated transistor leads. Clean the black residue at the gold - tin interface. Resolder the transistor leads after removing any gold left by tinning the lead and removing the solder a few times. Gold embrittlement is very common. 73 Glenn WB4UIV At 10:25 PM 8/19/2009, you wrote: Our club's MSR-2000 repeater recently ate it's PA, a TLD-2601A. Actually it went intermittent on us and several folks have gone over it with the magnifying glass and reflowed most of the major solder joints to no avail. That's a low split, 100 watt, continuous duty PA. If anyone has one available we are interested. We are in the Baltimore Washington area and could pick up within a reasonable distance (whatever the heck that is!) rather than shipping the fairly heavy unit. 73 de Tom/W4OKW (K3HKI Rpt) Yahoo! Groups Links
