On Fri, 04 Dec 2009 08:10:41 -0500, Blair S Balden wrote:
>I'm getting set to put up a wire dipole for 160 meters.
I love dipoles, and I have a lot of them (including a 160M dipole
at 120 ft), but a dipole at the height you're considering will be
a cloud-warmer on 160M. It's FAR too low as a fraction of a
wavelength to be a useful antenna for anything but local
ragchewing.
A FAR better option is some form of top-loaded vertical with on-
ground radials. Study the material in the ARRL Antenna Book on
both topics. Neither the antenna nor the radials need to be
perfect. With the radials, more is better, length is not critical.
With the vertical, length is not critical, more is better (to the
extent that it can fit on your lot). One form of this antenna is
the "inverted L." the other is a "Tee vertical." For all practical
purposes, they're the same antenna -- a vertical wire that you
can't make tall enough to hit a quarter wave, so you bend it
horizontally at the top to make it longer (the L) or in both
directions (the Tee). In addition to the added length, the
horizontal section adds capacitance to earth, which also helps get
closer to resonance.
The key parts of the antenna are the vertical wire near the
feedpoint -- this is what does the radiating -- and the radials.
The rest of the wire -- the top-loading -- simply brings it close
enough to resonance to get reasonable current distribution and an
impedance that your antenna tuner can match. (You WILL need an
antenna tuner).
Feed it with RG8.
73,
Jim K9YC
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