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[TowerTalk] Low Band Verticals

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Subject: [TowerTalk] Low Band Verticals
From: (
Date: Wed, 5 Sep 2001 09:00:20 -0600
In my original post on this topic, I pointed out that the
MFJ-1792 is FULL SIZE on 40M with an isolating / loading
coil (ON TOP) followed by a TOP HAT for a combination
of inductive and capacitive TOP LOADING on 80M.

The HF2V is also FULL SIZE on 40M but has inductive
BASE loading for 80M which reduces the current in
the element above the coil.

It is understood by the majority of knowledable antenna users
that end / top loading is much more efficient than inductive
base loading for the same overall length of radiator.

As N0AH points out, even Butternut, the maker of the HF2V
admits that adding TOP LOADING to the HF2V will make it
more efficient on 80M.  There is a limit on the amount of 
*capacitive* top loading that can be used without degrading
performance on 40M.  (This is why MFJ used a loading /
isolating coil between the 40M section and the capacity
hat.  It really is a BETTER design.)

Since the HF2V and the MFJ-1792 are close to the same 
physical size, it stands to reason that the top loaded 
MFJ 1792 would be more efficient on 80M than the
base loaded HF2V.  Experience with the base loaded
HF2V versus full size antennas shows it to be noticably 
inferior on 80M, even with a good radial system.

For some unknown reason, the MFJ-1792 is not highly 
advertised and promoted.  The HF2V has been around
for a long time and has been heavily advertised / promoted.
It was an early entry in the Low Band antenna game and
has performed reasonably well for a lot of people.  There
have been a few reports from very satisfied users of the
MFJ-1792 here on TowerTalk.  K4SQR reports that some
buyers of his 80M 4 Square box are using the MFJ 1792.

I just purchased an MFJ-1793, modified to include 30M,
and plan on installing it in a clear field where the nearest
metal object, a 12X24 storage building is ~150 ft (1/2 WL)
away and the nearest towers are ~300 ft (1WL) away.
I will compare it with my Elevated GP and tree supported
wire vertical and report back to TowerTalk at a later date.

Note that the MFJ 1792 is NOTHING like the NO RADIAL
MultiBand antennas they also sell.

Antenna performance (gain) is a continuom, not a discontinuous
black and white (BAD or GOOD) situation.  All I'm saying is that
I firmly believe the MFJ-1792  80 / 40 vertical is higher up the
gain ladder than the HF2V 80 / 40 vertical when it comes to 
performance on 80M.  Both antennas have limited bandwidth
on 80M due to loading effects.  The MFJ-1792 is a real bargain
at ~$150.

Tom  N4KG

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