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7 MHz antenna ?

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Subject: 7 MHz antenna ?
From: (rattmann)
Date: Wed, 18 Dec 1996 10:46:53 -0800
>Will a full-size horizontal dipole (one element beam) at 70 feet work better 
>my deltaloop ? (The deltaloop can not be turned around).
>At 60 feet I have a KLM KT34A - is 10 feet enough spacing and must the dipole
>be at 90 degrees off the beam ?
I presume the top of the delta is up around 55-58 feet, with beam at the
tower top on a rotator?  If so, I believe the rotating dipole up at 70 feet
(a half-wave high) will be significantly better that the delta loop.  It
will be more directive and you can take advantage of the movable pattern.
If you presently feed the delta with horizontal polarization, it is too low
to the ground to develop any useful gain, and is quite high angle.  If you
presently feed the delta with vertical polarization, you have substantial
reflective losses compared to the high dipole, and much of the low angle is
gone.  The computer model says the dipole should beat the loop by about 3
dB, and even more at the lower angles.  My own practical experience agrees
with this, since I have performed these comparisons at 80 meters but on the
same scale (half-wave high towers).

Regarding orientation... try it first the normal way.  Ten feet should be
enough to allow the KT-34 to work OK on 15m.  Maybe someone has modeled that
pair and could comment to you.  73!

Glenn K6NA

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