The longer inverted L moves the maximum current up into the vertical
section resulting in a higher feed impedance and more efficiency.
The higher the maximum current (to a point), the less loss in the
dirt. Further, the radiated field is proportional to the integral
of the current so putting the maximum current half way up the vertical
portion of the inverted L results in maximum radiated (vertical
polarized) field.
The effects of the higher maximum current and lower ground losses are
small - the latter depends on the "quality of the dirt" - but like
everything else with antenna systems, a fraction of a dB here and a
fraction of a dB somewhere else add up to real signal improvements.
73,
... Joe, W4TV
On 2018-10-05 11:11 AM, N4ZR wrote:
What to do when two respected references differ? ON4UN's book assumes
an Inverted-L is always a quarter wave ~135 feet), while the ARRL
Antenna Book assumes 165-170 feet. ON4UN mentions longer antennas to
increase feedpoint impedance, but doesn't seem to put much faith in that.
Comments?
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