I think your title says it, overload. Parelectronics makes a little 3 pole filter, is that the one you tried? You can tweak all 3 poles to 104.9 for about 50 db attnuation. http://www.parelectronics.com/vhf-fm.htm
A shorted stub would be easy to try too, there are several designs. Since the FM freq is so far away, try putting a T in line and a half wave (at 104.9) length of coax (times the velocity factor) on the T. Start long and work your way along the coax from the end with a pin and stick it in and short the coax while watching the FM signal on the spec anyl. Find the best null, then cut and solder and check the insertion loss at your 900 freq. ... Keith WE6R --- In [email protected], "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 >
