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

To: Jim Lux <>
Subject: Re: [TowerTalk] Problems on a 2el vertical Array
From: Tobias Wellnitz <>
Date: Sat, 10 Jan 2004 05:41:26 +0100
List-post: <>
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 <> triangle <>. At any time I'm using
two 2 verticals. This gives me 6 directions.
I can supply more informations (pattern, NEC files, messurements,

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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