David, Your problem might be harmonic related. Might do some calculator work. I can see no muliple of 104.9 related to your 2 frequencies or IF related.
There are other 900 MHz stuff around. Would be good to get a spectrum analyzer on your receiver port, but know spectrum analyzers are not easy to come by. Might be noise floor emissions from the FM station which could be on your receiver input. Now this one would be a real problem. 73, ron, n9ee/r >From: David Epley <[EMAIL PROTECTED]> >Date: 2007/11/22 Thu AM 07:32:46 CST >To: [email protected] >Subject: RE: [Repeater-Builder] Receiver overload > > >I just tried a pair of Celwave 8 inch bandpass cavities with no noticeable >improvement. > > >David N9CZV > >From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of >Jim Brown >Sent: Thursday, November 22, 20076:13 AM >To: [email protected] >Subject: Re: [Repeater-Builder]Receiver overload > >David,try using one or two band pass only cavaties in >the receive side instead of the BpBr type. The BpBr >filters often do not discriminate against signals far >off the pass frequency, and you may not be getting >enough rejection out of your input cavities. > >73 - Jim W5ZIT > >--- David Epley <[EMAIL PROTECTED]>wrote: > >> I have a repeater receiver overload problem I am >> trying to cure. The >> repeater is a 900mhz 927.7125/902.7125. There is an >> FM broadcast station 100 >> yards away 104.9mhz. The repeater works fine at >> another site. My transmitter >> is a Motorola Purc 5000 running 75 watts the >> receiver is a converted maxtrac >> 800mhz radio. Duplexers are Telwave BpBr 4 cavity. I >> have 10 to 12 db >> degradation when plugged into 3 different antennas >> on the tower. When I use >> a 900mhz dish antenna pointed away from broadcast >> tower I only have 3 db >> degradation. I have tried 3 different maxtrac >> receivers, added 2 more BpBr >> cavities in the receiver side and used 3 pole >> filters in the receivers with >> no improvement. Today I looked at the signal level >> getting to the receiver >> at 104.9. To my surprise I was getting -8 dbm at the >> 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. Any >> thoughts would be >> greatly appreciated. >> >> >> >> >> >> David Epley, N9CZV >> >> Winchester, Indiana >> >> > >__________________________________________________________ >Be a better pen pal. >Text or chat with friends inside Yahoo! Mail. See how. >http://overview.mail.yahoo.com/ > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
