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#11
October 12th 14, 09:12 PM
posted to rec.radio.amateur.antenna
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OK, let's discuss dipoles vs length
"Ian Jackson" wrote in message ... In message , writes Like I said, there is no difference in free space between a V and an inverted V. There are slight differences when close to ground. Assuming it's a halfwave dipole, I would have thought it was better to concentrate on getting the centre (where the current is) as high as possible, rather than the ends. [Obviously this depends on whether you have a suitable sky-hook available for and at the centre.] However, I believe that there is at least one commercial loaded dipole (essentially for portable use, I think) that has a short mast, and the ends of the V are up in the air. In free space I would not think there would be much of any differance. Near the ground where most of us are is what we have to live with. In my back yard I have enough room to string wire dipoles for 80 meters and shorter. I don't have a way to support the antennas in the middle. I can go up about 60 feet or so at the ends. One of my antennas is sort of flat as it is a windom and the long leg runs by my tower and was drooping to about 40 feet, so I put a piece of PVC pipe at the 50 foot level to help support it. The OCF antenna is suported so the ends are on some pulleys and a cinder block on the ground with a rope so that as trees swing the block will sometimes raise off the ground with high wind. I have put a spectrum analizer/tracking generator and return loss bridge on it a few times and watched the SWR/RL go up and down as the wind blew. Really interisting as the RL did not change much in amplitude, but the frequency shifted. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com |
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