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RE: Help needed with focal point - REPLY -



Jack, A couple things.
First, A helix feed is a VERY forgiving thing. I use a dual helix on my
portable rig. It is looking at a James Miller 60cm dish. Generally it is
felt that the best point to place the focal point is in the area if 1
1/2 turns on the helix, however my experience has indicated that you can
be anywhere from .5 to 3 or 4 turns from the reflector and still see
very little difference in performance.
Now, if the dish you are speaking of is a Channel Master Model 120 1.2
meter offset dish, you can go to my site and the full print of that dish
is there. www.wmfd.com/w8gsm
Good luck and see you on the bird.
73
Gunther Meisse
W8GSM


-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org] On
Behalf Of Jack O'Mara
Sent: Sunday, June 22, 2003 9:21 AM
To: amsat-bb@amsat.org
Subject: [amsat-bb] Help needed with focal point



Hi Folks

I have a 1.2 meter offset fed dish that I'm not sure of the focal point.
Does anyone use such a dish with a helix feed (5 1/4 turns) that could
tell me the distance from the reflector of the helix to the center of
the dish? This would then give me a starting point. I have tried
adjusting the focus but can't seem to see much difference. Any help
would be greatly appreciated.

Hope to work you all on field day. Listen for W4IY on AO-40.

Thanks and 73

Jack W4AD
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