[amsat-bb] Re: Antenna Polarization

i8cvs domenico.i8cvs at tin.it
Fri Sep 25 03:04:13 PDT 2009

----- Original Message ----- 
From: "Patrick Domack" <patrickdk at patrickdk.com>
To: <amsat-bb at amsat.org>
Sent: Wednesday, September 23, 2009 4:11 AM
Subject: [amsat-bb] Antenna Polarization

> I've been meaning to setup some antennas for satellite operation for  
> awhile here. And since I will probably end up doing it this  
> fall/winder I had a question I was wondering about, before I get the  
> antennas completely built connected up.
> I plan on using a circular polarized antenna, for lhcr and rhcr.
> Since this setup has two coax that your switch a 1/4wave (if I  
> remember right) to either side to create the two rotations in the  
> antenna.
> Is there a way I can modify this to feed two radios? so one radio  
> would receive lhcr, and the other rhcr? Or would I be forced to use  
> two antennas to do this?
> The only idea I have is to use a signal splitter on each of the two  
> antenna halfs before joining them, then join each of those splits into  
> the cr parts. But I'm not sure if there is a better way to do this  
> without as much loss, or if this might cause a backfeed that would  
> defeat the me from getting any signal at all.
> Maybe there is a good writeup of this on the web somewhere, but I have  
> no clue what the proper terms to google it are, and haven't had any  
> luck.
> Thanks.
Hi Patrick

What you propose to do is possible in theory but you need four 3 dB 
power dividers with characteristic impedance of 36 ohm each and 14
N/m male connectors so that the total losses of the system are too high.
I suggest to switch from RHCP to LHCP over the same receiver using
only a coax relay as described in all antenna books of the ARRL or into
"The Satellite Experimenter's Handbook by Martin Davidoff K2UBC
edited by the ARRL 

73" de
i8CVS Domenico 

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