[TowerTalk] Ring Rotors

[kq2m at kq2m.com]

Hi John,

I have two Rohn 45 towers (130' and 100') and four rotatable sidemounts 
(swinging gates) on the 100' tower which holds four Hygain HG105CA and 
four HG155CA yagis.  These are turned with T2X and Ham 4 rotators.

The sidemount at 37' used to stall during rotation because it was 
slightly off vertical and the TB3 above it was too tight, causing it to 
bind when it reached the same position each time.  If you can't get the 
mast perfectly vertical and the sidemount perfectly horizontal, what you 
can do is either substantially loosen the Thrust-bearing and keep it 
very loose or if you need more "play", you can remove the thrustbearing 
entirely.  That solved the binding problem. It was the one sidemount on 
which we did not use a level to ensure that it was perfectly aligned.  
That was an important lesson I learned and a mistake that I never 
repeated.  ;-)

Regarding rotation around a tower on a sidemount, normally you should be 
able to achieve 240 degrees minimum.  HOWEVER, with a little extra work 
and foresight, after you find the 240 degree rotation point, if you 
change the angle of the sidemount then you should be able to rotate it 
more around the tower; almost to 300 degrees.

When you get the sidemount in place, play with it instead of tightening 
it and you will see what you need to do to get that extra ~ 60 degrees.  
With ~ 300 degree rotation you will be close enough to almost any 
direction that you need.

Excellent idea using star guys.  I have two sets of star guys at 80' and 
120' on my big tower (which has no sidemounts yet).  I believe that the 
extra stability plus 6 extra guys is the only reason that the tower is 
still standing after two hurricanes (including Sandy with 120 mph wind 
gusts), three tornadoes and dozens of icestorms, Nor'easters and 
microbusts.

73

Bob, KQ2M



On 2023-01-30 18:54, John Webster NN1SS wrote:
> Wow. This is the first time I've posted here and I'm blown away by the
> number and quality of the responses.
> 
> Some more detail... The 404C sits just above a star guy bracket with 
> three
> sets of Phillystran 6700 to each guy anchor. You can see it in detail 
> on my
> QRZ page. As many of you have mentioned, a side mount rotor solution 
> has
> definitely been contemplated. I have a Rohn 45 top section that I'm
> thinking could be used if bolted to the tower. I did this once with a 6 
> ele
> 10m yagi and used a swinging gate to get something like 275 degrees of
> rotation. The problem I had with this configuration was, if the mast
> holding the antenna was slightly off vertical. the rotor would stall. 
> But
> that could have been fixed with a better rotor. I moved and took the 
> whole
> thing down so I never got to try that fix.
> 
> Short of using the ring rotor I'm probably happy if I can swing the 
> antenna
> in an arc between 45 degrees through to 270 degrees passing through 0
> degrees. That arc would give me EU, Asia and the US. I have an OCF 
> dipole
> on a 70' tower that works fine to the south. African mults are a bit of 
> a
> stretch but I can make it work.
> 
> At this point I'm thinking that I could make the Rohn 45 top section
> side-mount solution work if I mount it properly. I have to consider the
> star guy bracket that would be just under the antenna and I don't 
> really
> want to move the 404C any closer to the C31JK that is 10' above it. 
> There
> is already some interaction between the two antennas on 20 and 15 (the 
> 404C
> boom looks like a 20m reflector - something that is fixable but I don't
> want to make it any worse).
> 
> Anyway, that's where I'm at right now.
> 
> John
> NN1SS