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In article , "Scottm"
writes: Some of the parts, particularly the mechanical filters, can be hard to find. If the filters have detuned, as Bill eludes to in his posting, you'll suffer mild to excessive reduction in transmit audio quality. I have no experience with the HTs when it comes to filters, but have replaced several in the Collins S lines. Wow, I hadn't realized that mech filters (and maybe even xtal lattices?) can go sour with age. Presumably this would happen in receivers as well -- now maybe I know why some of my BA RX sound better on SSB than others? Though all are more than acceptable. Given a transceiver, where the same filters are used in tx and rx, if most received SSB signals sound good, cna you assume the tx side is good also? Not counting problems in the diver and final, of course. I have only one Collins set, a KWM-2, which makes any SSB signal sound terrific. I've had goon on-air reports from it, so I guess its filter is hanging in there. 73, Mike K. Oscar loves trash, but hates Spam! Delete him to reply to me. |
#2
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![]() "Mike Knudsen" wrote in message ... In article , "Scottm" writes: Wow, I hadn't realized that mech filters (and maybe even xtal lattices?) can go sour with age. I'm wouldn't say its with age, specifically, but use and mositure migration appear to be the culprit. I've opened bad ones up and found breaks in the tiny spot welds that attach the wire to the disks. I assume that either a good solid jolt (read UPS drop test) or the constant minute vibrations the filter experiences could do this. I have also opened them up to find moisture migration that has curroded or rusted the wire and disks. Any change in the spacings of the disks will dramatically change the filter's charactoristics. Presumably this would happen in receivers as well -- now maybe I know why some of my BA RX sound better on SSB than others? Though all are more than acceptable. Given a transceiver, where the same filters are used in tx and rx, if most received SSB signals sound good, cna you assume the tx side is good also? Not counting problems in the diver and final, of course. Yes. But sometimes it really hindges on the ear of the critic as well as the mic response. You can lose a couple hundred cycles on receive and still think that it sounds OK. You can lose a couple hundred cycles on TX and it will still transmit but not sound nearly as good as it should. This is particularly true with the S lines that use a 2.1 KC filter. You lose 200 cycles on the lower side and now your bandwidth is only 1.9 KC and sounds very tinny. Conversely, however, the opposite sideband sounds great because it has widened its passband. Also, when you transmit you are being compared against every other transmitter. When you receive, everyone is going to sound equally broad or narrow to you unless you compare it directly to another receiver. One final point, shifting of the 455 IF crystals can cause a similar result. If they drift off frequency, they will shift the IF. If they shift the lower too low or the upper too high it will cut part of the response the same way that a change in the filter will. I have only one Collins set, a KWM-2, which makes any SSB signal sound terrific. I've had goon on-air reports from it, so I guess its filter is hanging in there. The KWM-2 is a great radio. I have a RE 2A and love it. 73, Mike K. Oscar loves trash, but hates Spam! Delete him to reply to me. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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