[amsat-bb] Circular Polarity

[Ken Freedman <n1qqv@xxxxxxxxxx>]

Hi Gang,

      Today I bit the bullet and ordered an S-band down converter/preamp 
that has really nice specs.  That was the easy part.  Next I spent a couple 
of hours trying to figure out the polarity of the S-band hi-gain antenna on 
AO-40 so that I can start shopping for an antenna.  I  could find no 
polarity info for any antenna on AO-40 except the 70 cm arrangement which 
is RHCP.  I did find an article by G3RUH about how to build an S-band dish 
(got that tucked away on the hard drive!) for AO-13, in which he uses a 
helix at the feed, wound "opposite to a normal screw thread".

      I believe that a signal that leaves the bird from an  RHCP antenna 
would want to see an LHCP antenna on the ground, unless a dish were in use 
which would reverse the polarity on reflection to the focal point.  I think...

      There must be someone out there who knows the S-band antenna 
characteristics for AO-40.  Any help directing me toward the path of 
righteousness would be appreciated.  Especially at these prices!

TNX and 73, Ken

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org