>
> Not to defend the horizontal loop as a great antenna, but
there isn't much
> of a tendency to null on the horizon compared to a dipole
at the same
> height.
That's why full wave loops have low gain over a half wave
dipole. They generally have maximum gain in freespace. They
have near zero gain when installed at heights where ground
reflections already force a null where the 1/4 wl spacing
forces a null.
You can't have a large pattern change when you force a null
where an antenna system already has a null. To have useful
gain, we have to force a null where appreciable energy
exists.
All antennas work this way, it is pattern multiplication.
For example... if you model a 1 WL conventional horiz
polarized quad element (small null is straight up and down)
you'll see it has almost no effect at all being a quad when
at multiples of 1/2 wl mean height. The largest effect is at
odd multiples of 1/4 wl and with a single element quad.
> Mounted at 1 wavelength high, the signal at a 14 degree
takeoff
> angle is only down about 2 dB from a dipole along the line
perpendicular to
> the feedpoint while it's actually about 2 dB higher in the
minima off the
> "sides" compared to the signal off the end of a dipole.
I would expect that. But we were talking about a FW loop at
1/10th wl height, not one wavelength! We can't compare
things when off by a factor of ten.
At 1/10th wl height, it might as well be a dipole.
Besides heater applications in cold weather, loops have a
nice impedance on all harmonics compared to dipoles. Noise,
gain, and patterns aren't really a significant change at low
heights.
73 Tom
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