[UK-CONTEST] Rotator at foot of mast - any issues?

[John Lemay]

Hello Eddie

I've frequently put up multi antenna arrays on the sort of rotator you are
planning to use, and there have not been problems.

You may find that the motor begins to struggle if the loading is heavy, but
that is all.

The downward force on the rotator body is composed of two parts. The first
is easy to assess; it is the weight of your pole, aerials, cables, preamp
and so on.

The second part of the downward force is caused by the necessity of having a
bearing and guy ropes near the top, which stops the whole lot falling over.
Your guy ropes have tension in them, which you'll feel when tying them off
to some anchors. That tension is translated at the bearing into a horizontal
component which keeps things upright, and a vertical component which adds to
the downward force on the rotator.

So, it's good practice to keep the ropes tight, but not too tight.

When it gets windy (contest days of course!) there are additional forces
developed in your guy ropes, which add further to the downward force at the
bottom of the pole.

If you want to feel what is going on, try lifting up the pole after you have
guyed it. You might be surprised how "heavy" it seems to be.

Regards

John G4ZTR

-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com] On Behalf Of Eddie G0EHV
Sent: 28 May 2009 18:52
To: uk-contest at contesting.com
Subject: [UK-CONTEST] Rotator at foot of mast - any issues?

Hello,
In the past I've always used the "Armstrong" method to turn my mast when out

portable. It's a hassle when called by a weak one in a contest to jump out 
the car, turn the mast while listening to the radio then dash back to the 
operating position only to find he's QSY'd and is calling someone else!!
Now I have the chance to use a rotator - Kenpro KR-400.
I propose putting at the base of the mast. Anyone think of any issues with 
this? Mast is about 15 ft of alloy scaffold tube. Biggest antenna load at 
any time is a 2 Metre 13 ele yagi, plus a couple of 23 cms panels plus a 
couple of 13 cms loop yagi's.
I also will use a thrust bearing at the guy position.
Thanks,
Eddie
G0EHV
 

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