Monday, February 22, 2010

APRS Digi Repair

A few months ago, I had to work on my Local APRS Digi for the area, as the output levels were aparently in the Millawatts range. The power meter didn't even move when keyed. A few guys bought a Kenwood TM-271A for me to install, as it is a proven solid radio. The only thing I had to do was add a cable and solder it to the pads on the board inside the radio, as the American version doesn't have a TNC port. I salvaged an old PS/2 splitter cable, so it is the same plug as its Europian brothers.

When I arrived on site, the Site Owner said he had a new filter can for me, and as I began replacing the old radio and swapping the cans, I found a small puddle of water on the floor that wasn't there when I started.

Somehow water got inside the coax itself and was shorting out the radio, causing a high SWR (8), and minimal output. After I replaced the coax, I had an SWR of 1.75 to the ANTENNA antenna. After installing the filter can, it was 2. Not the greatest, but that antenna was tuned by messured length on the directions, vise actually tuning. It will be replaced soon with a higher gain antenna G7 anyways.

Because of the SWR of 2, I set the radio on High Power, of 60 watts. It only responds to Wide1 anyways, it mostly gates other digis in the Victor Valley and Antelope Valley.