[amsat-bb] Re HELIX REFLECTOR?

[Clare Fowler]

 To add to the discussion the July/Aug 2007 Amsat Journal has an article
covering some gain comparisonmeasurements I made between four
13 turn (2.88 wavelengths) 13cm antennas  with different square solid
aluminum reflectors.
The sizes were 0.56 wavelengths, 0.84 wavelengths, 1.0 wavelength and 1.4
 wavelengths.
There was no difference between the 0.84, 1.0 and 1.4 wavelengths but the
 antenna with the0.56 wavelength reflector had 1.5 db less gain.

 However for my 70cm helix antennas I followed the Satellite Handbook 
minimum
 size of 0.6 wavelengthsor slightly over 16 inches. I used 1/2 inch hardware 
cloth
mesh to keep the weight and windloading down.
These antennas have performed well however it appears that they would be a
 bit better with a somewhat larger reflector.

 A brief description and picture of the 70 cm reflector is in the
 November/December 2005 Amsat Journal article on
The Development of a Quarter Wave Match for helical antennas.

Clare  VE3NPC

>> Hi All:
>> I am rebuilding a 440 MHZ Helix that I built several years ago . It 
>> worked very well, but I would like to reduce the size of the reflector to 
>> a more manageable size than I had before. The only reference to reflector 
>> size I can find is, "minimum 20" ". I may be looking in the wrong places. 
>> I would appreciate it, if someone would steer me in the right direction.
>> Thanks,
>> Pete, K1HZU