[TowerTalk] control cables lightning protection

[K8RI on TT]

On 6/24/2011 1:15 AM, Kostas Stamatis wrote:
> Hello to all...
> I want to protect from lightning and static charges my rotator cable as a
> controller cable for a switch. I have seen some solutions in DXengineering
> but i would prefer a reliable homebrew solution. Anyone with some ideas?

Diacs were mentioned, but those are more of a control device.  Neon 
lamps (NE-51s) work well with tube input and control but are a bit high 
in voltage for rotator control.

For low voltage protection, I'd (1) keep the cables inside the tower and 
bypassed to the tower at the rotator and base of the tower.  The problem 
with solid state circuits is the need for a low clamping voltage.  They 
make some huge Zeners with a 3/4" threaded base which will handle huge 
current. Used are normally very cheap, but new are very expensive.  the 
nice thing about the big zeners is you can get one just a few volts 
above the maximum working voltage of the circuit. These are one place 
where I do favor MOVs.  As the rotator lines are low voltage and 
relatively protected by their very nature *IF* they are protected at the 
rotator and base of the tower the voltage is unlikely to rise very high 
and MOVs may last a very long time...but no guarantee.   The same with 
the massive Zeners.

There's the possibility of using 0.1 uf disk ceramics (You need a low Z 
at 1 MHz) on each of the leads at the rotator, and those or zeners or 
MOVs at the base of the tower and bulkhead connector at the station 
entrance.

I think most rotator damage comes from cable pick up, or from wiring 
pick up in the house with the current going back to the rotator.

73 and good luck,

Roger (K8RI)
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