[amsat-bb] Re: Turn off AGC when receiving BPSK-1000

[Art McBride]

Phil,

If you have access to the December 1970 issue of the Microwave Journal there
is data on a 1 wavelength, 1 turn Quadrifilar Helix with a beam width of
greater than 180 degrees. Only the 1/2 turn 1/2 wave is popular today, the
140 degree beam with offers the best front to back ratio @ 0.3 axial
wavelengths.
Art,
KC6UQH  


-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Phil Karn
Sent: Thursday, August 18, 2011 10:44 PM
To: Dave Guimont
Cc: amsat-bb at amsat.org
Subject: [amsat-bb] Re: Turn off AGC when receiving BPSK-1000

On 8/18/11 10:31 PM, Dave Guimont wrote:

> That's why the quadrifilars work so well. I measured the pattern some
> time back, and the "beam width" is about 140 degrees....

Yes, something with that kind of beamwidth would be ideal on the
nadir-facing surface of a stabilized satellite in low earth orbit. It
would be even better if the gain in the straight-down direction could be
reduced in favor of gain at the edges. Ideally you'd have a constant
power density over the entire visible earth.

You could of course use a much more directional antenna on the ground if
it can track the satellite.

--Phil


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