[amsat-bb] Helical Antenna for 2-meters

Edward R Cole kl7uw at acsalaska.net
Wed Feb 8 00:23:27 UTC 2017

Just scale the dimensions proportionally (except wire diameter);

ratio = 144/435

I built a 14 turn 437 MHz helical back in 1996 to receive the MGS 
beacon and built a 2.4 GHz 6-turn helical for 33-inch offset dish 
feed for AO-40.  Plenty information in Amsat Archives.  Original 
Kraus-W8JK design is optimistic in gain calculation.

W9EK had good construction hints in prior publications.

For receive-only do not sweat getting a good SWR.  I used a 1/4 
wavelength long 1/8 inch wide brass strip, run from connector to 
beginning turn of the helix for impedance matching.  Space the point 
of connection to the helix about 3/16 inch above the ground plane 
reflector.  Natural impedance of a helix is 140-ohm.

On air experience with the 432 helix was that a ten element CP 
crossed element yagi is better.  But if you desire CP the helix is a 
natural, though not perfect.

73, Ed - KL7UW
Dubus-NA Business mail:
   dubususa at gmail.com 

More information about the AMSAT-BB mailing list