A 3/8 wave wire will give almost as good performance
as the full halfwave. Of course, you have to use
balanced line to get the match efficiently. A good
number is 88', if you can swing it. This will give
satisfactory performance on 80 compared to a 1/2 wave
80 meter dipole. on 80M.(remember, most of the current
is in the part you kept, very little of your current
is sacrificed in the high voltage/low current ends you
trimmed off. Now, 88'is an Extended double zepp on 20
meters. So this length Doublet will give a broadside
pattern on all bands 80-20, without breaking into
lobes, and can be aimed in favorite, optimal
directions. It will cover the same DX area on every
band. ALSO, don't forget the knife switch! A knife
switch before entering shack, that disconnects the
feedline, and shorts it together for a voltage feed
connection, makes the set up operational for 80 meter
(and 160M if you have at least 65 ft. of feedline).
Your humble doublet, now becomes a vertical, top
loaded "T" antennas, with a low angle of radiation you
could never get from a dipole on 80. That's hard to
beat for a backyard antenna. A split lobe pattern
multi-wave on 10, 12, 17, a 20 Meter EDZ collinear
beam,a 30, 40, 60, 80 meter dipoles, and two low band
verticals. All in one small city backyard. Moreover,
no antenna interaction to worry about from akll your
antennas crowded in a tiny back yard. Ideally yopu set
uptwo of these spaced 90 degrees apart or so and cover
most directions. I believe the Take off angle on 20M
is 17 degrees with gain at my qth (65 feet up). It's
about that on 80 meters to if you set up the addition
voltage feed/knife switch arrangement. 66' and 44' are
also good if you don't have the 88 feet.
--- NJ0IP <Rick@DJ0IP.de> wrote:
> Ken,
>
> There is a magical length which is about 40 ft. per
> side (plus/minus a
> couple of ft.) that seems to work great on all bands
> (80 thru 10).
>
> I've put this type of antenna up at least 50 times
> at different locations,
> using all sorts of lengths due to space restrictions
> at some of the QTH's.
>
> Let me show you my "subjective" results I got using
> three versions, all fed
> with 450 ohm openwire:
>
> 1. 80m dipole (~65' per side)
> 2. Random doublet (about 40' per side)
> 3. 40m dipole (about 33' per side)
>
> #1 worked well on all bands and I could certainly
> hold my own in pileups on
> 80 and 40. Of course you lose out to the stations
> with the beams on 20 and
> above. Even matched on 160m with my matchbox, but
> was not very efficient
>
>
.
>
> Conclusion: Apparently you can reduce the size of
> the doublet up to about
> 35% without losing too much efficiency. Beyond
> that, you notice the
> difference.
>
>
>
> 73 ES ALOHA DE KH6/N6KB
>
>
>
>
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>
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