| Index | Thread | Archive | Jun-2002 | Archive | Send |
 |
  |
  |
   |
|
  |
|
Rain static, as I remember having read somewhere, is the result of each individual raindrop hitting the antenna. Each raindrop, according to the theory I remember, is water vapor that has condensed on a charged particle of dust. Therefore, each time a raindrop hits the antenna, it is accompanied by a bit of static charge. Regarding the clicking, I would surmise that this is static electricity arcing to earth from the locally charged atmosphere. It is definitely time to get away from the activity. Before my house and antenna installation were destroyed three years ago by the big Oklahoma tornado outbreak, I had never had a lightning strike on the tower, mast, and vertical 2m beam that reached 73 feet (22.25 meters). Neighbors, however, had reported FIRE flying off the antennas. I never saw it, but presume this was Saint Elmo's fire which was first experienced by the crews of sailing ships. This "fire" would sometimes fly around in the rigging for the sails. It is also occasionally seen by by aircrews flying in a highly charged atmosphere. While it is not necessarily a precursor of lightning strikes, it certainly signifies very high levels of charge in the local atmosphere. I would certainly take it as an indicator of a need to seek a more appropriate position. 73 - Mac, K2GKK/5 Oklahoma City, OK ----Original Message Follows---- From: Andrew Williamson <andrew@gi0nwg.freeserve.co.uk> To: Force12Talk@qth.com Subject: Re: [Force 12 Talk] Chirp-Chirp Date: Thu, 27 Jun 2002 19:18:41 +0100 In message <E17NLRm-0006r9-00.2002-06-26-23-40-35@imailm2.svr.pol.co.uk> , 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/ _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp. -------------------------------------------- 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 |
This Thread
|
This Author (Jun-2002)
|