Hi Kevin, The desense is a staticy reception of "weaker" signals( ie an HT at 25 miles) It had gotten worse as it started to affect strong signals too. If the transmitter was turned off, the repeater could hear just fine. Problem is intermittent and often followed a rainy day. We replaced "EVERYTHING" A UHF repeater on the same tower is unaffected. At this point we think the "new" antenna is failing. Tower sections have been bonded grounds improved etc etc In a message dated 8/8/2010 9:57:09 P.M. Eastern Daylight Time, kug...@kuggie.com writes:
_radi...@aol.rad_ (mailto:radi...@aol.com) wrote: Hi Kevin, I have confirmed that 2 of the 4 finals are bad. both are on one side of the push pull. Both open base connection One has collector to emitter short. The other open emitter. I have not yet checked the drivers I might be able to test them without removal. I have a friend trying to scare up a Mitrek Aside from the transistors which I know are hard to find, and the cooked 12 ohm resistors, Is there something else I need to look for? I doubt it. Usually the resistors go because of the imbalance from one or more of the transistors failing. I recommend replacing all of the output together with matched gain transistors, if you choose to repair the PA. We think it was an intermittent Duplexer or antenna issue that caused it to blow. We have since replaced the repeater, amp, and duplexer but a desense condition has returned after a few weeks. The antenna is a 4 bay folded dipole on a 100 foot tower. this Antenna replaced a Stationmaster only about 3 years ago. Tower is Rohn 45? guyed with Phillystrand. Thanks for your help. Marty What kind of desense? Does the repeater properly duplex on a known good dummy load? Kevin
