[Elecraft] Portable antenna

[k6se@juno.com]

W1CG wrote:

"I really can't explain why the vertical is so low noise (my house isn't
that noisy), and I would have guessed it would have performed a little
less well than the doublet and the vertical antenna with a fair number of
radials."

AA4LR wrote:

"Uh, that's easy. Your vertical is low noise because it is so lossy. The
two 2 foot radials are probably not doing much of anything, and you're
working against lossy ground.  Put 25-30 1/4 wave radials 1 foot off the
ground and you'll soon  find the antenna is much more noisy, but it will
be a lot more efficient, too."
==========
Although W1CG may not have a 100% efficient ground radial system, this
has very little to do with how his antenna receives.  Even if he is
losing 50% of his power into the ground, that means only 3 dB reduction
in received signal -- less than one S-unit.  His antenna efficiency is
probably much better than 50%, with the two radials being closer to the
ocean shore.

An example of how the soil conductivity over which the radials lie
effects the efficiency of the radial system is when I launched a
balloon-supported 1/4-wave vertical over a pure, moist salt ground for
the 160-meter CW contest last winter. With only four 1/4-wave radials,
the ground loss was only 2 ohms, for an efficiency of over 94% (ground
loss = 2/36)   If the same system was over "average" soil, the ground
loss resistance would be about 20 ohms, which results in an antenna
efficiency of only about 45%.

I also thought something was wrong with the antenna at the "dry" salt
lake location because the S-meter read zero on ambient noise (compared to
my S-7 nise at home).  Obviously however, the antenna worked, netting a
new division record in the ARRL 160 contest, world high in the Stew Perry
contest, and zone 3 high in the CQ WW 160 CW contest.

The proof of how an antenna works is how it gets out, and NOT how much
noise it receives.

73, de Earl, K6SE