> Hello to all,
> I am going to fly a Wire Vertical for 160 meters. The wire
will be held up with the use of a Balloon. I have done this
many times before. My >question is which antenna length
should I use,1/4 1/2 or 5/8 wave lenght.
A little slope generally doesn't mean much for pattern. The
elevation null associated with a 5/8th wave, gain, and the
main lobe angle is mainly due to current center height above
ground. The 5/8th antenna gets the gain of about one dB over
a 1/2 wave vertical, or 3dB over a 1/4 wl vertical, because
average current is higher above ground. If the top of the
5/8th wave blew over 60 feet, directivity would change less
than one dB.
The problem is you won't have infinite perfect ground, so
the 5/8th wave won't have 3dB gain over the 1/4 wave. This
is especially true if it is on a hill or elevated. A 5/8th
wave antenna can actually have loss over a 1/4 wl when the
flat perfect groundplane extending out a several wavelengths
is removed. If it is over excellent flat ground, it will
have too much elevation pattern compression for 160.
I have now and have used in the past what amounts to all
three antennas using insulated towers. With a good ground
system the performance difference on DX is not noticeable.
If anything a 5/8th wave antenna is slightly down for all
overall use, so I would avoid it even if it was perfectly
vertical. In A-B-C tests from here, the 1/4 wave or 200 ft
tower are about the same. The 318 foot tower is often
slightly weaker than the other towers. That's why my 318
foot tower is holding up dipoles.
73 Tom
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