Hi Steve, thanks for taking time out to help me solve this problem. I will try taking the aerial of the repeater RX to see what happens. The distance between antennas is about 20 feet. The FM antenna is circularly polarised, and the @ Meter is a DB224E with all diploes in line. Taking the FM transmitter off the air solved the problem. Re the duplexers they were tuned with a spectrum analyzer, the repeater receives signals as far away as 100 odd miles. I think it has been conclusively proved that the interference is coming from the FM transmitter. But I will make some more checks and see what happens, I will post my results. Thanks again guys.
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Steve Sent: Friday, March 05, 2010 8:14 AM To: [email protected] Subject: Re: [Repeater-Builder] Interference Pardon me for butting in again. Start with the simple things like taking the aerial off the rptr rx and see if that cures it. How far apart are the FM and rptr aerials, as it sounds like pure rf getting into the rx. Is the duplexer tuned right to give around 80db isolation as it maybe the rptrs own tx causing probs allthough he did say taking the FM,s aerial off cured it. Still recon my idea of a coax notch filter in the rx input will cure it. Steve ----- Original Message ----- From: Larry Horlick <mailto:[email protected]> To: [email protected] <mailto:[email protected]> Sent: Thursday, March 04, 2010 11:33 PM Subject: Re: [Repeater-Builder] Interference Is it IMD, though? Could it be in the audio chain? Leroy, did you troubleshoot from this angle? On Thu, Mar 4, 2010 at 12:53 PM, Leroy A. M. Baptiste <[email protected] <mailto:[email protected]> > wrote: Yes, they are. -----Original Message----- From: [email protected] <mailto:[email protected]> [mailto:[email protected] <mailto:[email protected]> ] On Behalf Of Larry Horlick Sent: Friday, March 05, 2010 1:36 AM To: [email protected] <mailto:Repeater-Builder%40yahoogroups.com> Subject: Re: [Repeater-Builder] Interference The 2m repeater and FM transmitter are at the same site? lh On Thu, Mar 4, 2010 at 8:56 AM, Leroy A. M. Baptiste <[email protected] <mailto:leroybaptiste%40spiceisle.com> <mailto:[email protected] <mailto:leroybaptiste%40spiceisle.com> > > wrote: Hello all, I am having some interference problems, it is coming from an FM transmitter on 94.500MHz, and getting into the Amateur Radio repeater's receiver on 146.1600MHz. It is not there all the time, but when the repeater is keyed up, you can hear it getting in. The 2 Meter repeater is fed with heliax cable from the duplexer to the antenna, the transmission line on the FM station is ordinary coaxial cable, the power output is about 300 Watts, any ideas? Leroy. J39AI
