Re: [TowerTalk] Problems on a 2el vertical Array

[Tobias Wellnitz <T.Wellnitz@gmx.de>]

Hi Jim & all,

thanks alot for your help. I'm just trying to write a little bit more
detailed document about my experiments with the verticals.

In order to conentrate on the main problem, I didn't tell that my
array was a little bit bigger.
I set up 3 verticals in a isosceles 
<http://dict.leo.org/?p=lURE.&search=isosceles> triangle 
<http://dict.leo.org/?p=lURE.&search=triangle>. At any time I'm using
two 2 verticals. This gives me 6 directions.
I can supply more informations (pattern, NEC files, messurements,
pictures...etc)

but let me just quote your comments:

> Close in contacts (or two bounce contacts) will have a high elevation angle,
> so the relative phasing of the antennas is not as optimized as for a low
> angle propagation.  Essentially, the antennas are closer together by
> cos(elevation angle).
>  
Right. Anyway, I should have in *all* situations more than 6dB f/b ratio.
(according to the antenna pattern)

> > Right now I have two possible answers / questions:
> >
> > 1. Is this the typical behavior of a 2el vertical Array ?
> >    
>
> If your measured data matches theoretical expectations within 3 dB, on an HF
> antenna over real ground, I'd be pretty happy.  Null depth (driving F/B) is
> the first thing to suffer.
>
> Consider also that the incoming wavefront is NOT a nice flat idealized
> wavefront, but varies with time and probably has local wiggles.
>
> Have you tried setting things up so you can swap front and back directions
> to measure f/b directly?
Yes, of course. I made two switching boxes:
1. 2el Array (2 switchable directions + single vertical)
2. 3el Array (6 switchable directions)

73 Toby, DH1TW

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