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Re: A naive helix/dish question



Message text written by "Freeman P. Pascal IV"
>
I'm putting together my 1m dish for use with mode L/S or U/S on AO-51. 
I started with a HighGain HG2424G and I added extensions to fill out the
perimeter of the dish so that it is a complete circle.  I have lined the
dish with 1/4" hardware cloth.

I am at the point I need to consider how to mount the 5 1/2 turn helix I
have.  The question I have is, do I mount the helix so that the far end
of the helix turns or the ground plan of the helix is at the focal
length of the dish? 

Also, are dishes and helix as easy as G3RUH makes them out to be?


-Freeman, N5FPP<
-----------------

The care and feeding of dishes is not a naive or trivial question! Instead
of 
answering the question directly (which would take a few pages),
 may I suggest that you Google and read Paul Wade W1GHZ's microwave antenna

book online. Outstanding stuff from a guy who has really dug into things.
He has 
whole chapters about feeding dish antennas. I know he recently wrote a
chapter about
use of helixes (helices?) but am not sure it is in the online book yet.

Are they easy? Yes, but follow the instructions closely. For a stand-alone
L band example,
see any recent Handbook (the most recent 2 years are a better physical
design) in the
satellite section under the article about an intgrated approach to L band
amp and
antenna. It was written for AO40, but the principles apply and the hardware
is useful.

73,
Ed K9EK
----
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