[amsat-bb] Re: Homebrew Polarity Switch

[HB9OMQ]

Dear David

In opposition of most common knowledge and post's of Ham's
you will not find much benefit in going circular.

If any antenna of a satellite is not pointing directly at
your antenna the polarization will be ellipsoid and not
circular.

I had a system to switch my antenna from vertical to horizontal
and circular left and right. Most of the time vertical or horizontal
polarization was best. When the satellite raises over the horizon
or sets to the horizon, horizontal will be best. Above some angle
vertical is better. During the pass the polarity may Change again.
Circular was at most as good as vertical or horizontal
but never better.

The switching circuitry to switch from horizontal to vertical is
only a single pole dual throw switch without any impedance transformation.
Much more easy to realize and much cheaper too.

The promised 3 dB Gain from a circular Antenna I never got.

Just a suggestion.

Paul

HB9OMQ

-----Ursprüngliche Nachricht-----
Von: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org]Im
Auftrag von David Wing
Gesendet: Donnerstag, 29. Juli 2010 07:42
An: 'AMSAT BB'
Betreff: [amsat-bb] Homebrew Polarity Switch


I’m looking into making a polarity switch for a ¼ wave offset crossed yagi
and am reviewing the write-up in the ARRL Satellite Handbook and the ARRL
Antenna Book (pretty much identical articles).  The diagram calls for a “1/4
wave 36 ohm transformer” as a part of the circuitry.  I’m having some
trouble finding anything like this online.  Is this a readily available
item?  Is it something I should plan on scratch building?  There is a
picture in the Antenna Handbook and the antenna includes this item and it
appears to be a manufactured part.



If anyone can point me in the right direction to find this item I would
appreciate it.  Additionally, if it is something that I could fabricate and
there is good info available online, please forward any appropriate links to
me.



Thanks,

David

K6CDW





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