[amsat-bb] Re: Helix Groundplane?

[kc6uqh]

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 at usna.edu>
To: "'kc6uqh'" <kc6uqh at cox.net>; <vk4tec at people.net.au>; "'Amsat-Bb at Amsat. 
Org'" <amsat-bb at amsat.org>
Cc: "'Aprssig'" <aprssig at lists.tapr.org>; "'ozaprs'" <ozaprs at 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
>