I think what this thread is about is effective, very lightweight
antennas for backpacking, SOTA, bicycle touring, etc. These are
antennas that, not including the support, weigh just a few ounces.
Whether they could be made to work better with hundreds of long radials
is completely irrelevant.
Without question, the EFHW minimizes resistive losses due to the high
feedpoint impedance, and eliminates the need for a feedline. If you
model a typical antenna of this sort, say a 66 foot wire with a single
38 foot support, and move the feedpoint around, you will find very
little difference in the far field. End fed is within a fraction of a
dB of center fed, and requires no feedline. Even 38 feet of RG-174
would weigh much more than a simple EFHW tuner, and the coax loss would
be about 1 dB on 20. Now, one could make some ladder line with some
number 26 wire and spacers, but imagine trying to get that untangled
every time you put up the antenna. (Another consideration: These
antennas should be quick and easy to put up.)
As I said, if anyone knows how to make a better, lighter antenna, let me
know!
An aside: There are two major loss components when feeding any antenna
near ground. One is due to the resistance which appears in series with
the feedpoint. (I'll call this the feedpoint loss.) The extreme example
is a short vertical fed against ground, where the effective resistance
of the connection to ground is large compared to the feedpoint
resistance. Raising the feedpoint resistance will reduce this loss, the
other extreme being the EFHW. The other source of loss is the
interaction of the electromagnetic field of the antenna with the ground
within some fraction of a wavelength from the antenna. Even a vertical
EFHW, with very low feedpoint loss, needs lots of long radials to
minimize this loss. Ideally, you want to minimize both sources of
loss. If a big radial system isn't feasible, it still helps to minimize
the feedpoint loss.
73,
Scott K9MA
--
Scott K9MA
[email protected]
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