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The earth
In article , NM5K wrote:
Yep.. I think the frustration tends to be difficulty in understanding that it's just one type of system, and others that do not require any ground connection do exist. Which means you would have to classify his statement as incorrect in the overall larger picture. I believe most have already stated that while some antennas do require such a connection, any "complete" antenna does not require one. Correct. One interesting counter-example, would be the simple one of a full-wavelength loop of wire, which is fed with a balanced feedline (twinlead or open-wire or ladder line), which is fed from a fully-balanced transmitter output stage (e.g. with transformer coupling from the driver transistors). To be extreme about it, let's say that the transmitter is itself based on a fully-balanced (differential) circuit, all the way back to the crystal oscillator. It's powered by a single battery, and is installed in a plastic chassic. This sort of antenna would have no galvanic connection to "earth" at all. Measure the resistance or RF impedance between any part of the antenna or feedline structure, and *anything* not part of the antenna, and the result will be "huge". Since it's a loop antenna, it has no "ends"... no points at which electrons could "fly off". The net current flow going up the feedline to the antenna will be zero, at all points - a positive current on one side of the feedline will be exactly balanced by a negative current on the other side of the feedline. There are no "excess" electrons or charge flowing in either direction. You can even insulate the antenna wires, if you wish. It will transmit just fine, with no connection at all to "ground". Disconnect the transmitter, install a receiver of a similar "balanced and isolated" design, and it'll receive just as well... again, with no connection to "ground". -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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