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On Aug 29, 10:38*pm, Roy Lewallen wrote:
Difficulty in getting power to an antenna is due to the mismatch between the transmitter and the impedance it sees, rather than between the transmission line and antenna. As a simple example, consider a 75 ohm dipole connected to a transmitter through a half wavelength of 600 ohm transmission line. /etc Rather than using an example of a balanced antenna having reasonably high radiation resistance and zero or low reactance at its input terminals, let us consider a base-fed 10 foot whip at 3.8 MHz -- which is more along the lines of this thread. Without using a loading coil, the input Z of that whip is about 0.6 -j 1250 ohms. The SWR that this antenna input Z presents to unmatched 50 to 600 ohm transmission line ranges from 52,167:1 to 5,340:1. Not much power will be transferred through such a match, which is the reason for the statements in my quote which you referred to. RF |
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