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VHF Antenna Recomendation
"Bruce in Alaska" wrote in message ... In article WN_Yf.1391$_u1.990@pd7tw2no, "surfnturf" wrote: While on the topic of antennas, what do you all think about the issue of RF exposure and the recomendation that omni directional antennas with a gain of under 9 dB be mounted 5 meters (15 ft) above deck level? Even the 1 meter above head level given as minimum height for the base of the antenna seems to be ignored on many boats. surfnturf RF Radiation is NOT ever going to be a problem on ANY non-commercial vessel. Period. None of the radiators that one can buy and install ever even come close to maximum RF Radiations Power Densities considered the Safe Levels. The same is true for most commercial Marine installations. My only concern would be to make sure that any MF/HF Antenna system be well insulated at any place where a person could come in contact with it. GTO-15 certainly would do this job for wire antennas, or a nonconductive insulating layer applied to any other antenna section that is within reach of a humans. The worst that could happen, should a person come in contact with the above, while transmitting, is that they could get an RF Burn, that is going to smart for a few days, but heck, an operator can get that, from a MF/HF Radio that doesn't have an adiquate RF Ground, from the Mic Hangup Button. Old Chief Lynn, will certainly testify to the above..... Military Vessels are a completely different can of worms, and they ALL have proceedures, and Operational Rules that are in place to protect operators and others who work in proximitry to the Radiating Surfaces. Bruce in alaska My humble opinion is that the radiation from the antenna of a 25 watt VHF transmitter probably doesn't do a person much good. However when considers how long the transmitting continues, it is probably nothing to worry about. (unless you have completely run out of things to worry about) How long do you hold the mic button down on an average cruise, anyway? Radiation from MF/HF transmitting antennas probably poses equally little to fear. But as Bruce points out, exposed wires and terminals can bite! And the smoke from RF burns on your nose, ears or fingers smells bad too. It would impress visitors to the radio room when the operator would hold a fully lit 40 watt fluorescent tube in his hands, with no wires attached. A lead pencil to draw RF arcs was much safer, and was a good indication that something coming out of the transmitter. And was a dandy tuning aid, too. Just tune for longest arc. Old Chief Lynn |
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