--- In Repeater-Builder@yahoogroups.com, "Leroy A. M. Baptiste" <leroybapti...@...> wrote: > > Hi Laryn, no I did not get a chance to answer your > questions, but here goes. The interference is > holding the squelch open on the repeater receiver > sometimes, which by extension holds the > transmitter on, or cycles it, based on the > interference into the receiver.
OK, this tells me that the interference is indeed getting into the receiver, not RF getting into the controller, or some other audio stages, for example. The interference > audio is not clean, it is distorted, the > interference is not always there when you key up. This sounds like it is the wideband (75 kc. deviation) FM signal getting into the receiver. Audio at that deviation will be VERY distorted, if heard at all. That's because it's so wide that there's little energy within your receiver's IF bandwidth much of the time. > Like I mentioned before, turning the FM > transmitter off cures the problem. Hope that > helps, and many thanks for your help. I haven't done any math on your numbers. There are several ways that the FM station's signal may be mixing somewhere with your transmitter, or even a third carrier may be involved in the mix. Locally, we have stations on 89.3 and 89.9, both mixing with our repeater output, to produce an intermod signal on our input. Like your symptoms, the signal was intermittent. Because two FM stations were involved, we had no noticeable interference until BOTH stations were transmitting very low, or no, audio. Such as spaces between words etc. Anything near normal deviation levels on either station would instantly close the receiver squelch and the problem was gone, for practical purposes. I found where the mixing was occurring with the aid of a spectrum analyzer, fed with a hand held beam. Guy wire turnbuckle "weave wires" were causing the mixing. I insulated them and problem is gone. Hope this helps. Good luck. Laryn K8TVZ
