[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Weighting Question on M2 2MCP22 and 436CP30

David Tipton wrote:

I am contemplating mounting my sat antennas on a shortened mast.  The booms 
on these antennas are like 12 feet long and I'm thinking about mounting 
them on my fiberglass boom at 3 feet from the Reflector end.

This will create a weighting problem as they won't be balanced.  What is 
the "Normal" method used to balance these out?

Wayne replies:

My 436CP30 is only 9.75 feet long, and my 2MCP14  is 10.5 feet long.  I
thought the 2MCP22 is 19 feet long!  (maybe you shortened it to 12 feet?)

If you add a loop of drooping coax, your 70cm antenna will be very close to
balanced when mounted 3 feet from the reflector.  The coax has a non-trivial
weight.   Also, the antenna is considerably heavier at the feedpoint end
because of the closer spaced elements, power splitter, phasing cables, and
folded dipole driven elements.  I'm not sure about your 2m antenna because
the length doesn't make sense to me.  You may need to add some weight if
your 2m antenna really is 12 feet long.  You probably don't need to add any
weight if your 2m antenna is 10.5 feet long like mine.

For several years I had my 2MCP14 and 436CP30 antennas mounted about 3 feet
from the reflector to achieve optimum balance with drooping coax loops.
After adding a heavy steel TranSystem BBQ dish I moved the yagi mounting
points 1 foot further forward to compensate for the weight of the dish.
That is, the yagis now have more weight "behind" the crossboom to compensate
for the weight of the dish "in front" of the crossboom.  The crossboom sees
some (irrelevant) torque, but the elevation rotor is balanced.

Wayne Estes W9AE
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org