[BC] Comtech Dish...

[Mike McCarthy]

One important question is whether the dish was laid flat or supported in
the middle. When you go to string check, measure the depth of the dish and
confirm the dish is still the correct parabolic curve/shape along equal
points of both axi and at 45 deg. offsets (total of 8 radials).  More than
1/4" deviation from expected and it's possible the dish is no longer round
or true from sitting in an unsupoprted position.

DH satellites are VERY sensitive to this and the instructions are very
specific about handling prior to the rear supports being in place and long
term storage.

MM

> Burt,
>
> That's interesting to know.  Has anyone else had similar problems with
> these?   Does the sag degrade its directivity in the azimuth plane, or
> just cause an elevation angle shift which can be corrected by cranking
> the bottom jack?
>
> We recently acquired a used Comtech 3.8 at an unbeatable price -- the
> cost of picking it up.  Surplus from a consolidation project, it had
> been disassembled, was stored indoors and appears to be in good
> condition, but before we spend money pouring the foundation, I would
> feel more comfortable if I knew that it hasn't sagged appreciably.
> At least I'm planning to put the reflector back together and pull two
> strings across the rim just to see how close they meet before we
> proceed.
>
> If we invert the mounting 180 degrees, might this help the sag to
> "cancel out" over time?
>
> We plan to replace a 3.0 m Harris Cassegrain (was it AP or UPI that
> once used those?) which is marginal on AMC-8 but works better than I
> expected at our Western NY location.
>
> Mark