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Re: primestar ??



The f/d's are very close on both of those dishes, if a 5.5 turn helix works 
on one, it should work on the other.

Gain is proportional to area with parabolic reflectors (dishes).

Lets "swag" this.... If you were illuminating these 100%:

The oval (36x26-- which you probably only illuminating part of or over 
illuminating the other part)-- 936 sq/in
The "1.2" (54X48) -- 2592 sq/in

2592 / 936 = 2.77 times larger.... 10 log (2.77) = 4.42 dB greater gain.  
About half the Beamwidth more or less.

You'll likely illuminate the 54x48 more efficiently with proper tweaking.  
So I'd do a rough estimate of gaining an "S-unit" on AO-40.

Your windload will go up (I believe) square of the extra area or 7.6 times 
the force.  (someone correct me if I'm wrong on this)

So that's the tradeoffs.  I really like the larger P*/Muzak dishes I have, 
but I've been a bit chicken to mount them on a G-5500.


Fred W0FMS


>From: w7lrd@juno.com
>To: amsat-bb@AMSAT.Org
>Subject: [amsat-bb] primestar ??
>Date: Sun, 12 Jan 2003 09:21:29 -0800
>
>Hello
>I am currently using the small (36X26) primestar dish with a 3731.  I
>have a 1.2M (54X48) primestar dish.  I am considering putting the 1.2 to
>use.  Questions are:
>Can I use the same 5.5 turn helix for a feed?
>How much more gain will I realize?
>Do any of you have the 1.2 in use?
>
>73...Bob...W7LRD
>Seattle
>----
>Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
>To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org


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