Re: [amsat-bb] P3D X-band antennas

[n8kwx2@xxxxxxxx]

Good general P3D 10 GHz info:

http://www.rats.fi/suomi/amsat-oh/phaseima.htm


or more specifically:

http://www.rats.fi/suomi/amsat-oh/images/p3d_oh_3.jpg

This is a picture of what you are interested in...

The bottom item is a rectangular to circular waveguide transition with an
attached circular horn antenna.  The sets of screws that you see are used
for tuning (matching) of the waveguide and generation of circular
polarization.

I forget the exact mechanism, but I believe that the first row excites a
linearly polarized mode in the waveguide and the next row excites another
mode orthogonal to the first (at the correct phase) creating circular
polarization.  Much like the phased and crossed dipoles of a "turnstile"
antenna.


These are all from the excellent webpage:

http://www.rats.fi/suomi/amsat-oh/amsat-oh.html

of the Finnish AMSAT group.


73,

Marc - N8KWX






on 11/8/00 2:31 PM, Richard W L Limebear at Richard@g3rwl.demon.co.uk wrote:

> Jim Sanford writes:
>> Question:  What did we use to achieve circular polarization on P3D's X
>> and Ku -band antennas???
> 
> We didn't. My understanding is that these are linear polarization.
> 
> 73
> Richard W L Limebear G3RWL
> g3rwl@amsat.org
> FOC # 1188
> 
> So many beautiful girls ..... (sob) so little time
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