[amsat-bb] Small Dish and Helix w/cup

[K5OE@xxxxxxx]

Okay, it's Mark Hammond's fault, who asked me how I attached the helix feed 
(earlier email).  I had not attached it--only held it out in front of the 
dish :-)  Surely I had something around here I could scrounge up to support 
this thing?  Luckily, I had some 1-1/4" steel angle left over from my 
4x28-turn helix project and used a piece of it to attach the helix w/cup and 
Drake, put it up on the rotator, just in time to listen to UO-11 on a 10 
degree pass.  I heard it about 6-9 dB above the noise (wav file available on 
request).  What is important, however, is I have never heard UO-11 below 
15-20 degrees before with a helix!  This is a very temporary installation 
(see the pix below), so I guess I will be up at 1:30 AM when AO-40 comes over.

If you are wondering why I started down this path, it was because I thought 
if I could reduce the typical helix reflector diameter, you would gain more 
use of the dish--not blocked by the big reflector.  With a small dish like 
this, that is even more important.  This cup design is only 66 % of a 1.0 
lambda reflector and a mere 44 % of the typical 6" reflector.  The final 
spacing was 12" to the back of the coffee can.  Mark is right:  this is fun!

Here are the pix:
http://members.aol.com/k5oe/helix_cup01.jpg
http://members.aol.com/k5oe/helix_cup02.jpg
http://members.aol.com/k5oe/helix_cup03.jpg
http://members.aol.com/k5oe/helix_cup04.jpg
73,
Jerry, K5OE
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