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R: Cross Boom



Hi All,

Mounting a crossed yagi for CP in X or + configuration over a metallic
boom produces the same effect over the circularity.

When two crossed dipoles are feed by the same amount of power but their
components are 90 degrees out of phase the resultant vectors of voltage
and current rotates by  2 x 360 x f  every second producing CP

The rotor of a AC sincronous motor rotates by the same phisical principle
of magnetic rotating field discovered by Galileo Ferraris.

Try now to put your finger in to the squarrel cage of the motor in both
X or + position and see what happen to it !

Your FINGER or your METALLIC boom are the same thing.

73" de i8CVS Domenico

----- Original Message -----
From: Roy Welch <rdwelch@swbell.net>
To: hasan schiers <schiers@netins.net>
Cc: <amsat-bb@AMSAT.Org>
Sent: Thursday, March 06, 2003 9:54 PM
Subject: Re: [amsat-bb] Cross Boom


>
> hasan schiers wrote:
> > I participated in the original discussion of this many months ago and I
> > think that the article referred to is being "under quoted". It is NOT
just
> > mounting the antenna in the "X" configuration. That is NOT what the
article
> > says. It also REQUIRES careful placement of the driven element distance
to
> > the cross boom. Doing the "X" alignment is a "necessary" but not
> > "sufficient" condition to get the results that the article claimed.
> >
> > Two conditions have to be met:
> >
> > 1. X configuration
>
> The article does say this.  Mounting the elements in a + configuration can
> "see as much as a 10db loss in gain and the circularity would be nil."
>
> > 2. Distance from the feed to the cross boom
>
> The article does say to avoid mounting the boom 1/2 or 1 full wavelength
> from the driven element.
>
> As a third requirement the article says to "saw off any excess cross
boom."
>
> I think I said all three of these in my original reply.
>
> > Many people have testified anecdotally to the metal cross boom working.
The
> > work of the WA5 in the article made careful measurements. I wouldn't
> > hesitate to try it, but follow the instructions in the article
assiduously.
> > The half-baked representations I have seen discussed lately are unlikely
to
> > produce the "tenths of dB" performance hit described by the original
author.
>
> The author's test was done about 1993. I have used this configuration
since
> 1981 or 1982.  It has worked fine here and I have had reports of it
working
> fine for others.
>
> > My comments aren't to discourage the metal cross boom approach. The
article
> > convinced me. However, let's not forget the second requirement.
>
> I didn't omit the second requirement.
>
> > ...hasan, N0AN
>
> ----
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----
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