[amsat-bb] Re: Help and advice needed

George Henry ka3hsw at earthlink.net
Thu Jun 14 21:04:06 PDT 2007

One of the best tricks is to insert a length of wooden dowel into the ends 
of the crossboom, so that you can crank down the clamps tightly without 
crushing the boom.  Some people also cut the boom in half and then re-join 
the halves with another length of wooden dowel, to strengthen the center of 
the boom where the rotor clamps tighten down.  I have never found the need 
to do anything more than the dowel in the boom ends to securely tighten the 
antennas to the crossboom, and have never had slippage problems with the 
rotor clamps, either.

As far as the feedline goes, conventional wisdom says that having the 
feedline pass through the pattern of the antenna (at 90 degrees to the boom) 
anywhere forward of the reflector distorts the pattern, so the best option 
is to hang the feedline off the back of the boom.  Secure it to the mast 
below the rotor, with enough slack to allow the antennas to turn through the 
full 360 degrees of azimuth and 90 (or 180) degrees of elevation.  My own 
experience with a couple of different brands and lengths of CP antennas has 
been that any distortion caused, has never kept me from hitting or hearing 
the satellites...  your mileage may vary, however.

George, KA3HSW

----- Original Message ----- 
From: "Rolf Moberg" <oh6kxl at sral.fi>
To: <amsat-bb at amsat.org>
Sent: Thursday, June 14, 2007 2:57 PM
Subject: [amsat-bb] Help and advice needed

> I'm planning my station. I need some advice from more experienced
> satellite operators.
> My rotator will be Yaesu G5500. 70cm antenna is 3m long helix and 2m
> antenna wil be 2.4m long Wimo cross yagi phased for circular polarization.
> I've planned to use 3m long glass fibre boom. Antennas will be attached
> to boom ends. They sell a boom with 40mm diameter and 2mm wall thickness.
> What kind of solutions you have to create more friction to the junction
> between antenna boom clamps and boom? And another point is where G5500
> boom clamps are attached to boom center. Should I cover those four
> places with some metal strips?
> And last. 70cm flexible feeder will be installed back of the helix plate
> and then to the boom. 2m is a question. Should I run rg213 feeder via
> yagi boom to the fibre glass boom? Or should I let rg213 feeder go to
> the reflector end and make a loose loop towards to glass fibre boom?
> Rolf Moberg
> oh6kxl

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