[TowerTalk] Fw: Topband: Top Loading of Shunt-fed Tower

[Joe Subich, K4IK]

Tony, 

> > I assume the StepIR uses an aluminum boom. I wonder if 
> > there is there any chance of arc-over from the boom to 
> > the motor circuits with high voltage induced at the top 
> > of the tower/boom when loading on 160M?

Not likely ... with the control wires taped tightly to the 
boom, the RF voltage induced in the control wires will be 
very close to that in the boom.  The differential will be 
small enough so as not to pose a problem.  

The motors are isolated from the BeCu tape ... the shaft of 
the sprocket assembly is an insulating material.  Thus if 
the parasitic elements are retracted there is very little 
capacitance to couple (and develop a voltage differential) 
across the shaft.  The safest course of action is to take 
a piece of 1/2" wide aluminum or copper flashing and connect 
between the contact assemblies of the "outside" parasitic 
elements (reflector and last director) and the closest 
mounting bolt. 

73, 

   ... Joe, K4IK