Scott, Please elaborate on the "old age" problem. Are we talking about the wear and erosion that results from endless "pumping" of the center tuning element which, however slight, moves during cycles from cold when idle to warm after long transmissions? That's about the only cause of a poor contact I am aware of. Whenever I found this problem, reversing the TX/RX tuning fixed it. When you found that reversal did not help, what was your diagnosis?
73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Scott Overstreet Sent: Thursday, November 08, 2007 8:54 AM To: [email protected] Cc: Scott Overstreet Subject: Re: [Repeater-Builder] 2 Meter Duplexer Recommendations? Hello Tony If we are talking in the 2 meter ham band---read on. The PD 497 series duplexer is a very good duplexer until old age sets in-----I have two of them here that have gone noisy---I should say that mine produce wide band noise when transmitter power is applied----lots of desense in spite of looking perfect on the tuneup instruments-----and they are not easily fixed----and a Tx/Rx reversal didn't help. In my case, space is tight---the 497 is shorter than most and replacement with a standard Telewave catalog unit was impossible at the low end of 2 meters . A little pleading with Telewave resulted in their making a special for me that fit nicely in place of the 497 and very nearly equaled the 497 performance which was more than enough for my application. If you are concidering a new duplexer---I suggest that you call Len Pringle (KH8A) at Telewave (1-800-331-3396) and ask about the "2 meter Ham Special" ----their PN TPRD-14556 that he had built for me. ----- Original Message ----- From: Tony L. <mailto:[EMAIL PROTECTED]> To: [email protected] <mailto:[email protected]> Sent: Wednesday, November 07, 2007 8:10 PM Subject: [Repeater-Builder] 2 Meter Duplexer Recommendations? My Celwave PD 497-1-1 VHF duplexer just can't seem to provide adequate tx/rx isolation (Micor 100 watt repeater with 0.6 MHz tx/rx separation). Everything else seems to check out okay; jumper cables, connectors, receiver, and hard line. I've heard the PD 497-1-1 isn't the latest in duplexer design and was wondering what other VHF repeater owners might recommend with regard to high performing, closed spaced duplexers for moderate power applications. Thanks.
