Is it really necessary to isolate the vertical from the pressure treated 4
x
4 with PVC tubing and is it really necessary to install a 1:1 balun
between
the antenna and feedline in this 4-square receiving array?
In this case the antenna was base loaded and pretty short (30 feet = .05
wavelengths), so anything around the antenna above the base loading can have
a large effect. It really should be spaced a few inches away from any wooden
pole because the impedance and electric field is so high.
If the impedance was lower, it could be nailed right to the pole with no ill
effects. It has almost nothing to do with leakage resistance. The problem
really is the poor and grossly changing dielectric near the high impedance
area of the antenna.
It is always a good idea to fully isolate the feedline when using a small
radial system, or when fairly strong common mode noise is present on the
feedline shield.
73 Tom
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Topband Reflector
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