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@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Phil Karn Sent: Thursday, August 18, 2011 10:44 PM To: Dave Guimont Cc: amsat-bb@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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