Bob, The bottom side of the helix is the opposite rotation, the screen as you pointed out is a counterpoise that determines the driving end and the radiating end. I have also phased two helixes one LH and one RH for linear polorization. You can get more gain than a yagi at 1.2 GHz using this configuration. 3 db for phasing + 3 dB recovered for linear.
Art, KC6UQH ----- Original Message ----- From: "Robert Bruninga" bruninga@usna.edu To: "'kc6uqh'" kc6uqh@cox.net; vk4tec@people.net.au; "'Amsat-Bb@Amsat. Org'" amsat-bb@amsat.org Cc: "'Aprssig'" aprssig@lists.tapr.org; "'ozaprs'" ozaprs@aprs.net.au Sent: Tuesday, December 11, 2007 3:49 PM Subject: Helix Groundplane?
Helix antennas being circulary polorized have rejection to the opposite rotation generaly caused by reflections provided that both...
Wow, interesting. I just realized then, that the "reflector screen" at the back of a Helix is not adding any gain then. Because it is true, that any reflected energy will be the opposite circularity! Thus it cannot add in phase to the direct wave.
I guess all the ground plane is doing is providing a counterpoise for the feed system. Oh, and possibly a degree of attenuation to ground noise... Both well worth the metal, I guess. Comments?
Bob, WB4APR