My favorite "dipole" antenna is a 20 meter extended double zepp, fed with
balanced line (450 ohm ladder line for home use or 300 ohm twinlead for
portable/qrp operation). At 44 feet per leg, it can be set up as a
horizontal doublet, a sloping doublet or an inverted vee. What you end up
with is an 88 foot doublet.
For best feedline balance, run the feedline perpendicular from the
horizontal or sloping doublet. For the inverted vee, run the feedline at
equal angles from, in between and in the same plane as the two legs of the
antenna. Of course, the geometry of your yard and location of trees may
limit your ability to run the feedline in this manner. Just do it as best
you can, trying to keep the feedline perpendicular or equi-angular for at
least a half wavelength at 20 meters, if possible.
You can feed such an 88-foot doublet with an antenna tuner (for a remote
tuner add a 1:1 coax choke balun on the input side of the tuner and at the
transceiver, for internal/shack tuners add a 4:1 current balun on the
output side of the tuner -the Elecraft BL1 works well for this application-
and keep the coax line from the tuner to the balun as short as possible,
just long enough to keep the balanced line out of the shack or away from
the transceiver, but preferably no longer than 20 feet maximum).
Such an antenna system, with a decent antenna tuner, will usually load up
nicely on all bands, 80 through 10 meters. On 20 meters, it gives about 3
db of bidirectional gain over a dipole. On 17 meters, the pattern becomes a
cloverleaf, with more lobes sprouting out as you go to shorter wavelengths.
On 30, the bidirectional gain is about 1.6 db over a dipole. On 40, the
antenna's pattern and gain is similar to a dipole and on 80, the pattern
begins to become omnidirectional, with a reduction in bidirectional gain.
For more details, go to http://www.cebik.com/88.html
No room for an 88-foot doublet? Willing to forgo 80 meter operation? Try a
70 foot doublet (35 feet per leg). That's an extended double zepp for 17
meters and a slightly long 1/2 wave dipole on 40. It'll work well on 40
through 10. You can even get by with a 44 foot doublet (22 feet per leg),
if you don't mind pushing the 3db extended double zepp advantage to 10 meters.
73,
Martin
W7MJM
At 02:51 PM 8/5/04 -0500, you wrote:
The Windom is not a cure all antenna, and indeed has a number of potential
problems...
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