Re: [amsat-bb] CP v Linear polarisation

[Dave Guimont <dguimon1@xxxxxxxxxx>]

>
>In 1983, DL1BU et al did a series of controlled experiments using the
>real-world signals from the beacon of Oscar-10. The full results were
>published in "VHF Comms" in the Autumn issue of that year. The tests
>involved a number of antennas which were instantly switchable. They included
>linear horizontal, linear vertical, 45 deg. linear, 135 deg. linear, RHCP
>and LHCP. The tests were conducted at both high and low satellite elevations
>and at times around apogee and perigee. Quite a complete and impressive
>test. The test results came up with three clear conclusions.
>
>1/ although there were some rare and unrepeatable circumstances when linear
>pol. yielded slightly better signals, overall switchable R/L CP was the best
>by far.

Thank you, Bill for all that good information.  I'll add some fuel to the fire.

With my "garage engineering" I built a 4 element circular quad:

Bicycle Wheel Quad THE ARRL ANTENNA COMPENDIUM VOLUME 1 p. 18

The driven element is rotatable 90°, and a pull on a fishline in the shack
gives me all angles between H and V.  It was built in 1984, and I compared
ALL the degrees of linear polarization with a KLM 22C that was switchable
from RHCP  to LHCP to vertical to horizontal.

There were various results at various AZ/EL's, but the biggest differences
occurred at low EL's.  I certainly have no way to measure absolutes, but
RHCP prevailed 90% of the time.  LHCP, at times, would pull out signals no 
longer
readable with RHCP and/or ALL degrees of linear.  Again with the exception
of signals at or near the horizon.  My antenna "looks" at the ocean  from
about 180° to 350°, and the terrain is relatively flat for the remainder.

I took down all the "garbage" it took to switch the 22c in the four modes, and
made sure the relay was wired to give RHCP in the event of a relay failure.

I never pay much attention to transmit.  Of course that will make a difference,
but one can always "turn up the wick".

Tnx agn...

            73, Dave wb6llo@amsat.org
                    Disagree: I learn....
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org