Bruce, I suspect that there are a couple hundred desktop and laptop computers in that office building, and any one of them can be radiating a carrier or a harmonic thereof that falls on or near your input frequency.
A case in point: I was tuning up an GR1225 repeater a while back when I noticed that the "receive" LED was blinking without any sound coming from the speaker. When I disabled the PL decode, I heard a slightly off-frequency carrier that was very weak, but just strong enough to open the squelch. After sniffing around with a portable scanner, I found that the source was my 900 MHz Athlon computer. My later 1.2 GHz computer did not radiate any carrier that I could detect, but a more recent 2.6 GHz computer does radiate a carrier- but it doesn't fall on any radio channels I use. Almost any device with a CPU inside can be an unintentional radiator, even a microwave oven or a sewing machine. In an office building, devices like copy machines, motion detectors, wireless modems, and similar devices are candidates. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of lpcoates Sent: Friday, November 09, 2007 9:02 PM To: [email protected] Subject: [Repeater-Builder] Possible interference on 146.160 Hi Our radio club has a portable repeater on 146.760 (-). Each time we install it on a commercial building we find what appears to be interference on or very near the input frequncy of 146.160. This repeater was installed at two private homes for several weeks each and worked flawlessley. Tonight it began to act up after just a few minutes. Another repeater was tried at one of these commercial sites and it also appeared to be receiving interference on 146.160. Tonight I tried a simple test of tuning my hand held to 146.160 and found several "hot spots" in the room where I picked up something as well as picking up something radiating from the electrical conduit. Both of the commercial sites have elevator equipment, one quite old and one very modern. One site hosts several other radio systems from 400 MHz to 10 GHz and the other site has not other radio equipment. Both buildings are 12 story office buildings. My question is, have other people found that this frequency is especially prone to interference from nearby electrical and electronic equipment? I know that the output frequency of 146.760 can be a problem because it's very close to the 41nd harmonic of the colorburst crystal, but I haven't been able to find any mention of problems on the input frequency of 146.160. Thanks Bruce - VE5BNC
