On 8/13/2017 10:32 AM, Walter Underwood wrote:
Without the wire on the ground, the chassis is the other terminal, like your
BC-459 (previous message), but also includes your body when you touch it, which
changes the impedance of the antenna system.
Yep. But in a vehicle, the VEHICLE'S chassis is the return. That's how
mobile antennas work. And at home, an end fed wire with no radials uses
the power system in your house as the counterpoise. While this can work,
it also puts RF in your house and picks up noise from your house. And
our body is the return for the antenna of our VHF/UHF talkie.
On 8/13/2017 10:22 AM, Barry wrote:
Jim,
You got it. That is why my first recommendation is for ground
independent antennas. For portable use, any antenna that can be hung
by a single support should work nicely so long as it approximates 1/2
wave on the lowest frequency.
There's a gotcha there. It's quasi-ground-independent ONLY when there's
a current minima at the feedpoint, and it isn't easy to make a single
wire do that on all bands where we want to operate, because some are not
harmonically related, and because a half wave is pretty long on 80 and
40M. :) And when it's an end fed full wave or 3/2 wave, the resulting
pattern is pretty loby. But it is certainly true that when we CAN rig
and load an end-fed half-wave, it's a pretty efficient antenna,
especially if it's vertical.
73, Jim K9YC
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