OK, this is probably not going to be an easy one. I have seen several instances of mast-mounted TV preamps oscillating and acting as miniature transmitters capable of sweeping over wide swaths of spectrum as the temperature changes. They usually exhibit a raw AC buzz on the signal. They are almost never active when the weather is cold, only coming active as the ambient temperature rises. Usually were fed with twin lead. Your description of the audio seems to put that possibility pretty far down the list.
At this point I would probably want to look at the incoming signals on the repeater with a spectrum analyser and see if you can quantify the level of the incoming interference signals. If the interference level is high enough you should be able to hear it and maybe track it with a service monitor that can be run off of 12v in a mobile. Since you can call a number on one of the transmitters you can control things a bit. Good luck hunting. Milt ----- Original Message ----- From: Mike Besemer (WM4B) To: Repeater-Builder@yahoogroups.com Sent: Saturday, April 24, 2010 4:42 PM Subject: RE: [Repeater-Builder] Re: Pager Interference Revisited Milt, Not sure what you mean by 'come and go'. It's there when the pager transmitter is up, gone when it's not. It also comes and goes with heat and sun. we may have days with no interference if it's cool and cloudy or just plain cold. Rain makes no difference. Nothing remarkable about the audio. sounds like clean, clear paging tones. Never heard anything els There is an abundance of TV stations, DTV, translators, AM, FM. you name it. The paging signals are both, depending on which site it's coming from. I can get my hands on pretty much anything I need. Spectrum analyzer is no problem. I have a good 'connection'. Did some hunting with a spectrum analyzer last year to no avail, but now that I have the ability to call the system and have it send out a page we have a little better advantage. I'd call the area 'populated', but not 'urban'. Mostly housing around the site, but plenty of industry (and towers) visible from the top of the water tank. (We are, by the way, the only user on the tank.) From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Milt Sent: Saturday, April 24, 2010 4:19 PM To: Repeater-Builder@yahoogroups.com Subject: e: [Repeater-Builder] Re: Pager Interference Revisited Mike, Does the interfering signal come and go or is it constant? Does it have any AC component; ie buzz or hum at 60Hz, 120Hz, etc., or any raw buzzing noise? Are there any broiadcast TV stations in the area, DTV or LP translators? Is the UHF pager signal analog, digital or both? What test equipmet do you ahve available? Is the repeater in a poplulated area or remote? Milt N3LTQ ----- Original Message ----- From: Mike Besemer (WM4B) To: Repeater-Builder@yahoogroups.com Sent: Saturday, April 24, 2010 3:36 PM Subject: RE: [Repeater-Builder] Re: Pager Interference Revisited I don't think so, Chuck. I work on Robins and traverse it pretty much from end-to-end daily. I also have to traverse it quite a ways just to get off of it to go foxhunt this beast. Generally the signals on-base are weak to non-existent. It's bloody amazing how much RF crap is in the air. Using a Google Earth application I can see zillions of sites within earshot. The mixing possibilities are endless! I'm somewhat surprise that we've never heard any audio mixing in with it. 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Saturday, April 24, 2010 3:16 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Pager Interference Revisited How close is Robins AFB? Maybe? Chuck WB2EDV ----- Original Message ----- From: Mike Besemer (WM4B) To: Repeater-Builder@yahoogroups.com Sent: Saturday, April 24, 2010 2:48 PM Subject: RE: [Repeater-Builder] Re: Pager Interference Revisited Given that the interference is in three different repeaters over about 40 air-miles, I have not done that. I've THOUGHT about it, but it didn't make sense, give the circumstances. 73, Mike WM4B
