David, As suggested in another post a bandpass cavity might be in order.
You idea of a stub, open ended 1/4 wavelength coax, will probably help. Just have to make sure it don't affect your 900 MHz signal, but would be cheap thing to try. I have 2 m repeater antenna about 100 ft vertically from 2 100 kW ERP, 40 kW RF, FM stations. I have no problem and bet if I sampled on my antenna I would have enormous level from them. If over load from the FM carrier it should be simple to solve. 73, ron, n9ee/r >From: David Epley <[EMAIL PROTECTED]> >Date: 2007/11/21 Wed PM 10:03:29 CST >To: [email protected] >Subject: [Repeater-Builder] Receiver overload > > >I have a repeaterreceiver overload problem I am trying to cure. The repeater >is a 900mhz927.7125/902.7125. There is an FM broadcast station 100 yards away >104.9mhz.The repeater works fine at another site. My transmitter is a Motorola >Purc 5000running 75 watts the receiver is a converted maxtrac 800mhz radio. >Duplexersare Telwave BpBr 4 cavity. I have 10 to 12 db degradation when >plugged into 3different antennas on the tower. When I use a 900mhz dish >antenna pointed awayfrom broadcast tower I only have 3 db degradation. I have >tried 3 different maxtracreceivers, added 2 more BpBr cavities in the receiver >side and used 3 polefilters in the receivers with no improvement. Today I >looked at the signallevel getting to the receiver at 104.9. To my surprise I >was getting -8 dbm atthe receiver. I believe this level is overloading the >front end of my repeater.I was wondering if a stub cut for the broadcast >frequency would work. Anythoughts would be greatly appreciated. > > >David Epley, N9CZV >Winchester, Indiana Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
