Saturday, July 21, 2007

Amateur Radio: A funny thing happened on the way to the contest today...

Just a quick note on a funny story; at least one of those ones that radio amateurs find funny.

Most amateurs have stories about RF (especially in the HF bands) causing trouble around the house. Usually just simple TV interference, harmless stuff. One guy I knew said his digital bedside clock would reset itself when he transmitted on certain frequencies. Another said his stereo would turn on by itself. I've heard my external hard drive park its heads during transmit, and in general USB hardware doesn't seem to like RF.

I've been dealing with some "RF in the shack" lately; because until I can get my heavy coax run back up to the roof I'm operating on a somewhat hacked setup. Specifically; at anything below 20 meters I get feedback paths into my audio, and one night I got "bit" by one of the screws on my radio's casing. (Caused by signals inducing currents into the radio itself.) Typical symptom of a grounding problem, and expected considering my current setup. I decided to try out an artifical ground; which is essentially like an antenna tuner between the station and ground. It provides a tuned circuit that electrically lengthens or shortens the ground, and it can even be used to make a random wire stretched along the floor act like a ground.

So as I fiddled with the artificial ground settings on one band I keyed up and as I did I heard my sprinklers come on. Maybe my wife's working in the garden, or...? I key up again, same thing. Apparently I was kicking out enough power to activate the driver transistors in my sprinkler controller and this is what caused them to turn on.


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