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: [email protected] [mailto:[email protected]] On Behalf Of Daniel "Nick" Kucij Sent: Thursday, July 29, 2010 9:11 AM To: [email protected] 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 links to 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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