Dirty paging TX. Seen that many times. Joe M.
Mike wrote: > A couple of weeks ago, our repeater system started to experience interference > from a paging system. The repeater is on 146.850 (-600 KHz), with the > antenna system about 120 feet up a water tower. The repeater itself is an > Advanced Communications System KRP-5000 running 35 watts through a set of 4 > WACOM cans. The feedline is 7/8" hardline feeding a DB-224. All jumpers are > RG-214 MILSPEC with MILSPEC connectors. This system has been in service for > years and has never given us any problems, and we are the only ones at the > site. > > To be clear, the interference we are experiencing is clearly audible on the > repeater input. I have the capability to monitor via telephone and have > heard it on the receiver, and I've also traveled to the site and heard the > interference on my mobile radio hooked to the repeater antenna. The > interference is also audible on the input in various locations around town. > Also, the interference can be heard on the input regardless of whether or not > the repeater transmitter is on. It also continued to be present during > several days of continuous heavy rain. > > The interference typically shows up at least once a day, although some days > (rarely) it does not show up at all and other days it will show up several > times. Lately, it's been making an appearance around 10 a.m. and hangs > around for an hour or two. As it begins to disappear, it sounds as though it > is moving off frequency. > > This interference has also been heard on at least two other repeaters in the > area. One is about 22 air-miles from the 146.85 machine and is on 145.110 > (-600 KHz). It has also been heard on or near the output frequency of that > machine, and one evening I tracked it from about 145.120 to 145.190 as it > swept through each transmission. The other repeater it has been heard on is > 147.300 (+600 KHz). I also have reports from a neighboring county a > ham/deputy sheriff there has been hearing it on VHF public safety > frequencies. As you can see, it's all over the place. > > I've been working with the owner of a local paging company and we can clearly > tell that the data we're hearing is coming from 152.480 and 462.775. He has > two sites (about 20 miles apart) that simulcasts on both frequencies and when > those transmitters are active it's easy to tell that the data is the same. > He also tells me that he can key each transmitter separately and the data > from each transmitter will be heard on our repeater. We also believe that > there are other systems on nearby frequencies that are being heard on our > repeater, specifically 462.850 and 462.925. > > I've run IMD numbers on everything I can think of, but can't come up with a > common thread. For it to be moving all through the 2-meter band and for it > to be mixing with several different frequencies, it seems to me that it's got > to be very ugly and unstable. What am I missing here? > > Mike > WM4B > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
