[Antennas] Alpha Delta DX-EE, NOT an inclement weather antenna

[Philip]

Hi All,

Awhile back I installed an Alpha Delta DX-EE antenna along with a couple 
inverted Vee's for 20 and 15M.  The Vee are at right angles to, and off the 
end of the DX-EE and there doesn't appear to be any interaction between 
them, at least not so that you'd notice.

The DX-EE is a "shorty" four band fan dipole for 40, 20, 15 & 10 meters. 
There are three wire elements on each side, one for 40/20M, one for 15M and 
one for 10M.

The element for 40/20M is basically a 20 Meter dipole with a large "Iso-Res" 
(loading) coil on either end, then a short piece of wire after the coil to 
resonate on 40M. Naturally it has a very narrow bandwidth on 40M.

When I installed it, it resonated towards the bottom end of the 20 & 40 
Meter bands, fine with me as the tuner tunes it just fine and I can live 
with it.

HOWEVER, IT HAS A MAJOR PROBLEM.  When wet (like it gets rained on) the SWR 
goes so high on 40 & 20M that the MFJ auto-tuner CANNOT match it, and this 
tuner seems like it'll match nearly anything, including a wet noodle. . . 
15 and 10 meter operation is essentially unchanged.

As soon as it dries out some it will match just fine.  I DON'T believe that 
it is water in the coax (RG-213) as it is well sealed and recovers far too 
quickly for that.  Also, 15 & 10 meters would be bad if that were the case.

It appears that the problem MUST be in the Iso-Res (loading) coils on either 
end of the 20M element.  These are close-wound on what appears to be PVC 
pipe, then coated with a UV protectant varnish of some sort.  They are NOT 
enclosed in anything, so the actual coil winding gets wet.  While that 
probably wouldn't affect the actual inductance, it IS probably affecting the 
inter-winding capacity (close-wound).

Although it doesn't affect 15-10M much, at least not out of the tuning range 
of the tuner, it's a pain in that when it occurs my only recourse is to 
switch to the Roof mounted Butternut HF-2V vertical for 40M operations. 
It's better suited for DX operation than "in-state" net operation.  (The 
Alpha Delta, being rather low over the metal roof is good for NVIS operation 
on 40M).

IDEAS anyone?   It doesn't appear that it'd be very easy to enclose/pot the 
coils as that would almost certainly change the tuning of the antenna and 
once enclosed it'd be difficult to change the length, at least of the 20M 
element.

73 de Phil,  KO6BB
DX begins at the noise floor!

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