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Date: Sat, 03 Jun 2000 19:32:13 +0100
To: rsgb_lf_group@blacksheep.org
From: "Walter Blanchard" <blanch@pncl.co.uk>
Subject: Re: LF: Re: Aerial tests.
In-reply-to: <000301bfcc87$d6d381a0$9dd699d4@w8k3f0>
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At 13:41 02/06/00 +0200, you wrote:
>To All from PA0SE
>
>Walter Blanchard quoted the RACAL expert who has in the past  designed the
>Decca antennas as follows:
>
> >(...)  If the small one has an assymetric horizontal component (flat-top)
> > this will complicate matters considerably since it will radiate both
> > vertical and
> > horizontally-polarised and there will be interaction between them that
> > will affect the radiation pattern. So it would be unlikely to have a
>circular
> > polar pattern and this might account for some of the observed variations.
>
>This is not confirmed by computer simulation.
>
>Computer program AO by Brian Beezley, K6STI, shows  for the L-antenna over
>medium ground  an almost perfect omnidirectional radiation pattern. The
>deviation
>from a circle is no  more than about 0.1dB.
>
>The program also shows that the maximum of the horizontally polarised wave
>is straight up and 21.1dB down on the maximum of the vertically polarised
>wave.
>The latter maximum occurs under an angle of 12 degrees (direct + reflected
>wave).
>In the region where the inverse distance law is applicable the space in the
>vertical radiation pattern between  zero degrees and the lobe under 12
>degrees is filled by the surface wave.

Dick,

I haven't got AO so could you see what it says about the following:

An inverted-L half-wave resonant at 1950 kHz, vertical section  25m high,
horizontal  55m long.  What does it predict the VERTICALLY-POLARISED
horizontal polar pattern to be ?
I know the answer, because I've measured it, I just want to know what
your AO says!

Walter G3JKV.