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Fwd: Mode S feed for TVRO Dish

To the person asking for helix feed size for his dish, I repeat what I sent
earlier this year:  This recommendation is valid for f/d from 0.3 to 0.4
and workable up to 0.5 but with some dish edge spillover.  For f/d > 0.4
start adding more turns to the helix.  For my 18 inch RCA DSS dish the
effective f/d is 0.7 and that requires a 5-turn helix.  Coffee can horn is
only good to f/d 0.4. 

>Date: Tue, 30 Jan 2001 16:56:35 -0800
>To: amsat-bb@AMSAT.Org
>From: "Edward R. Cole" <al7eb@ptialaska.net>
>Subject: Fwd: [amsat-bb] Mode S feed for TVRO Dish

>Most TVRO dishes are f/d ratio of ~.35, so either a 3-turn helix or a 1
pound coffee can horn will work.  Ten feet is pretty large for satellites
at 2.4 GHz and will have a narrow beam width requiring precise pointing.
But if you can do it you'll have no problem with the signal.>

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