Scott, When you say "3 cavity" do you mean three total, or three on each side? If the former, I suspect that the duplexer has insufficient isolation and/or your transmitter has some spurious output. Take a spectrum analyzer to the site and monitor the off-air signal with a short whip to check the purity of your transmitted signal.
Your comment about things being different when you're at the site brings to mind an interesting case from the past: I remember one site that had several repeaters, and *some* of their owners complained that the systems worked fine normally, but went bonkers while a technician was at the site. But, get this: The remaining owners complained that their systems were bonkers normally, but worked fine when a technician was at the site! After a great deal of head-scratching, it suddenly dawned on us that the only thing that changed when a technician was at the site was that the interior lights were always turned on, since there were no windows in the radio building. The one switch for the interior lights also turned on some big outside floodlights, in case the visit was at night. The problem turned out to be a bad neutral connection at the last pole before the drop to the radio shack. The poor neutral connection allowed the center tap of the 120/240 VAC circuit to shift toward the side with the heavy load of the lights, and we measured about 102 volts on one side and about 135 volts on the other. When the lights were off the shift went the other way. Occasionally, the splice would weld itself and the problem would go away for weeks at a time, only to reappear during a windy day. This is a very common problem for utility linemen, because aluminum wire is often used for long overhead lines, but copper is used for the house drop. A special "bi-metal" splice should be used at the junction, but sometimes that gets missed during emergency restoration work. Just to be certain that power is not an issue, use a good DVM to measure the voltage at your repeater. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Scott Sent: Wednesday, December 28, 2005 7:14 PM To: [email protected] Subject: [Repeater-Builder] Mitrek 70CM problem Well, here is the setup, and the problem: Setup: Moto Mitek trunk mobile on 70CM with CAT 250 controller, and control head intact (mic disconnected). TX-RX duplexers (GE flavor, 3 cavity) retuned. Uses stock tone board for incoming tone, Com-Spec board for outgoing. Running about 25W into duplexer. Problem: Worked OK for a month in the shop on a small antenna, about a day at the site, then now the RX audio is not there unless you are at the site. Also you get a wierd growling like feedback and cycling of the TX for a minute. Suggestions: ?? Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> 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/
