# [amsat-bb] Re: Re; Homebrew Polarity Switch

Art McBride kc6uqh at cox.net
Sat Jul 31 09:14:57 PDT 2010

```Nick,
The circuit you referred to can be simplified. The two 1/4 wave 75 Ohm coax
sections match the two antennas to 50 Ohms. A 1/4 50 ohm line will delay the
signal by 90 degrees for circular polarization. The opposite rotation is
accomplished by adding of a 1/2 wave 50 ohm section to delay one side by 180
degrees. Further simplification when using crossed Yagi's is to space one
Yagi a 1/4 wave behind the other and use only the 1/2 wave section.
The end result is to have one antenna lead or lag by 90 degrees for RH or LH
rotation.
To make this work both antennas must be the same electrically and any feed
line after the matching sections must be identical lengths to the antennas.
All wavelength calculations use 2952/frequency in MHz times the VP of the
coax for a 1/4 wave in inches. Multiply by 2 for 1/2 wave.
Experiment and build your own.
Amateur radio is learning by doing!

Art, KC6UQH

-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Daniel "Nick" Kucij
Sent: Thursday, July 29, 2010 9:11 AM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Re; Homebrew Polarity Switch

> 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
> me.
>
>

David,

PA3GUO has described a homebrew switch on his website,
http://www.pa3guo.com/
Click on Antennas, then scroll to the Polarity Switch button.

Nick KB1RVT

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