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# Re: 2..4ghz dishes

• Subject: Re: [amsat-bb] 2..4ghz dishes
• From: Joseph V Murray <k0vty@xxxxxxxx>
• Date: Mon, 19 Feb 2001 10:30:25 cst

```Hi Jerry

Thanks for a good complete answer.     There was a ham years ago that
used an antenna that had a rotor on the boom of a linear yagi for AO-13
work.      He was able to turn the boom to sense the polarization .
I only know from very many QSO's that he seemingly never had a problem .
I do not know how often he had to turn the boom.
Give this some thought one day while your taking nap.

Thanks again

Joe  K0VTY
=========================

On Mon, 19 Feb 2001 07:39:59 EST K5OE@aol.com writes:
> Hi Joe.
>
> > If you are reporting on the use of a circular polarized ( helix )
> and a
> >  linear polarized antenna ( BBQ dish).    What "S" units do you
> attribute
> >  the difference in the polarization ?
>
> I have no way to measure the difference (right now).  As you know,
> theory
> states 3 dB is the delta, but that assumes from a perfectly circular
> to a
> perfectly linear signal.  And (another big AND), conventional wisdom
> is an
> S-unit is worth 6 dB.  Thus, if the world was perfect, the answer
> would be
> 1/2 S-unit difference.
>
> It is doubtful the signal received from AO-40 is either truly linear
> or
> circular--but more likely a slowly changing elliptical signal.  I
> noted when
> AO-40 had the 2 m telemetry beacon turned on, it would change from
> RHCP to
> LHCP over a few hours time.
>
> A good way to measure this delta might be for someone with a dish to
> swap out
> the feed from a linear one to a circular one.  It might also be
> instructive
> to note the difference between a LHCP and RHCP feed.
> 73,
> Jerry, K5OE

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