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Re: S-Band Dish



>From: "Deon Erwin" <zr1dq@qsl.net>
>Our local satellite TV dishes are inexpensive and lightweight.  The feed arm
>is located off-center, but the dish is symetrical (round) with a diameter of
>1200mm.  The LNB frequency is about 12GHz.  I can obtain the focal point
>information.
>
>How useable would the dish be on the S-band?

Deon,

This sounds like an offset feed dish.  The size, 1.2m, should work real
fine.  The P3D examples from Amsat use 60 cm dish and ~20 dB SNR.  Does the
feed arm come from the side of the dish?  If so, I would say it is an
offset-feed design.  The focal point will not change going to 2400 MHz.
However, depending on the type of feed you chose, you will need to adjust
its position to get it optimized at the focus.  F/D ratio on offset dishes
are about 0.7.

I plan to use an American ku-band sat-TV dish [DSS] which is 18 inch.  That
is about 43 cm.  My plan is to construct a dual S/X band feed for
receive-only {I described it recently in another message}.  My latest plan
is to mount the dish with my 432 antenna on a roof-top tripod.  Thus it
will be ready for modes US and UX.  My 1296 antenna is co-mounted with the
2m array on a 40 foot tower; all will be on az-el mounts.  

I also have a 2.5m dish which is being set up for 3 cm eme.  I may use it
for mode-X, too.  Of course with a .79 dBNF preamp it will hear AO-40
extremely well.  Keeping it pointed will be more difficult.

Quite gratified to see the number of stations getting ready for the
microwave freqs!

73, Ed
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