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[TowerTalk] C31XR & XM-240

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Subject: [TowerTalk] C31XR & XM-240
From: (
Date: Mon, 23 Aug 1999 15:15:47 -0600

On Mon, 23 Aug 1999 14:19:34 -0700 (PDT) mohammad almutairi
<> writes:
>I have recently purchased two new antennas. The Force 12 C31XR &
>Cushcraft XM-240.I am planning to put both antennas on the same tower
>mast. I have read somewhere that positioning the antennas 90 Deg of
>each other helps eleminate any interaction between them , how true is
>that ? . The part of mast sticking out of the tower is 9 ft long. In
>what arrangement should the antennas be arranged in?, who's on top?.
>With regards to spacing the antennas is the 9 ft sufficient.
>The tower is about 60 ft high.
>The rotor that will be turning the  antennas is the HAM IV .
>The weight of the C31Xr = lb 82   W/L 10.5 Sq.Ft
>The weight of the XM240 = lb 55   W/L  5.5 Sq.Ft
>The mast weight         = lb 40
>Total                   = lb 177
>Is the HAM IV rotator capable of rotating the 177 lbs mentioned 

I have a similar setup, a big KLM tribander just above the thrust
bearing, and a 40-2CD Cushcraft short 40 just 6 feet above the
tribander. The booms are in-line, not rotated 90 degrees, and
everything works very well with no interaction that I can detect.
I put the antenna with the biggest windload at the bottom of the

I have used both a Ham IV and a Tailtwister on this array at
different times. The Ham IV seems to last about 2 years, and
the Tailtwister lasts about 4 years. Weak points on the Ham IV
for me were the 1/4 inch u-bolts, and the self-tapping screws
(tapping into aluminum) that hold the two castings together. If you
have a choice, use the Tailtwister.

Dave Hachadorian, K6LL
San Diego, CA

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