[TowerTalk] Problems on a 2el vertical Array

[Tobias Wellnitz]

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