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"ku4yp" wrote
in reference to station grounding, i have read keep the grounding strap as short as possible and not a multiple of a resonant length on the ham bands. (etc) __________________ Unless your antenna requires an earth ground as an integral part of its design, the length or number of ham band wavelengths, or even the existence of a metallic path to earth is irrelevant to the radiation characteristics of the antenna itself. Still, a good earth ground and other means are desirable to protect your equipment from lightning transients, as developed by Jack Painter on his informative website link earlier in this thread. Here is a re-post of some earlier text I posted about the need for an "antenna ground." GW asked (clip): How do you determine the quality of an antenna ground at HF on an absolute basis? Not how well have I maximized what Mother Nature gave me at my QTH by adding radials, but how good is my ground compared to other stations' grounds at other locations? A low-resistance ground connection for a transmit antenna is important to the received signal level only when the antenna design requires it as a reference for its driven element, such as with the vertical radiators used in MW broadcasting. Most HF/VHF/UHF transmit antennas do not need, or use an earth ground for efficient radiation. As practical proof of this, recall that airborne antennas have no connection at all to earth ground, but still work just fine. And the transmit antennas used in commercial FM & TV broadcast are installed at the top of a tall tower, many wavelengths (and ohms) above earth potential. The tower is grounded for safety reasons, but the radiation patterns and received signal levels from those antennas would be the same even if that tower was not grounded. RF Visit http://rfry.org for FM broadcast RF system papers. |
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