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

[Andy Cook, G4PIQ]

I've seen KR400s used to turn vertical stacks of 4 x 17 element 2m yagis
from the bottom of 60ft scaffold pole masts and they do this OK - at least
in a temporary portable situation. The biggest risk seemed to be applying
too big a bending moment across the rotator and cracking the mast clamp, but
your situation is much lighter duty. 

73,

Andy, G4PIQ



-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com] On Behalf Of Chris G3SVL
Sent: 28 May 2009 18:05
To: uk-contest at contesting.com
Subject: Re: [UK-CONTEST] Rotator at foot of mast - any issues?


At 18:51 28/05/2009, Eddie G0EHV wrote:
>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.

Eddy,

The issue to think about here is the vertical weight sitting on the 
top of the rotator. This will be the sum of the weights of the mast 
and any antennas.  I suggest you estimate those weights and look at 
the KR-400 spec to make sure its OK. You will need to guy it high up 
to avoid lateral loads which would be a killer (i.e. a small movement 
at the top will generate a big lateral force at the bottom).

I use a rotator at the bottom of the mast here - but its a bigger 
antenna and a bigger rotator.

73 Chris, G3SVL

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