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, Francisco Costa <fcosta@mail.telepac.pt> writes >Hi All > >About two weeks ago, the day before I went on holidays, >as usual, I disconnected all antennas from my radios. >(This allow me to have a more relaxed vacation :0) >Without coincidence, later that same day, very dark clouds >sudenly appeard and promised a storm. But despite some >rain drops, no thunder or lightning was observed. >However a (very) wierd thing was noted: when those dark >clouds were forming, on my back yard a strange sound >come out of no where! >First it sound like a "clik", but then sounded more like a >"chirp". The cadence wasn't constant, but during a brief >period it was less than a second, like: "chirp-chirp-chirp". >I look around for the source of the sound and it lead me >to my new self suported 15m tower. On top there are >3 antennas: 5 elem 6m and 21 elem 2m yagi from Tonna, >and a Force 12 C4XL. I was about to climb to the top >to check exactly the origin of the sound, but for obvious >reasons I gave up the idea. Even so, I'm preety sure the >sound came from the C4XL. But I don't understand why! >I never have "seen" this kind of efect on an antenna. >Have you? Do you have a reasonable explanation for this? >If you, I really apreciate your help. This sounds very familiar, most likely a build up of static electricity. I have experienced something like this whilst standing on the top of a 100ft tower. It happened a few minutes before a heavy rain shower, so I'm guessing that charged air was preceding the rain. The first thing I knew about the charge was when the driven element of a 15M antenna we were installing (at that stage without feedline) started to arc across the split driven element (about 0.5"). It started clicking slowly and built up to quite a fast rate of arcing (approx 4-5 clicks/second). Shortly after that I felt quite big shocks every time I touched the tower (though I didn't get shocked if I maintained skin contact with the tower). It felt quite similar to touching an electric fence that a farmer uses to keep cattle in a field. Quite scary really because the first thing that went through my mind was that this was the build-up to a lightning strike. And I certainly didn't want to be 100ft up a tower if lightning struck. Needless to say, I got out of there fairly quickly!! Having heard the rate of arcing at the feedpoint, I wonder is this what generates 'rain static' in the receiver? The arcing would certainly have been generating broadband noise at quite a high repetition rate. Andrew Williamson GI0NWG / AC6WI Homepage = http://www.gi0nwg.freeserve.co.uk/ One of the ZL9CI gang http://www.qsl.net/zl9ci/ -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |
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