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: [email protected] [mailto:[email protected]] On Behalf Of Phil Karn Sent: Thursday, August 18, 2011 10:44 PM To: Dave Guimont Cc: [email protected] 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 _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb __________ Information from ESET NOD32 Antivirus, version of virus signature database 6391 (20110819) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __________ Information from ESET NOD32 Antivirus, version of virus signature database 6393 (20110819) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
