[TowerTalk] Vacuum variable / inductor ratings for shunt fed tower

[K4SAV]

N6RK wrote: "I spent a lot of time analyzing the balun in my MonstIR and 
characterizing it on a network analyzer."

I have always wondered how well that thing worked.  They use half of the 
core for a voltage balun and they use the other half for a choke by 
winding a few turns of the coax thru it.  What does your measurements 
tell you about how well the common mode choke works?

Jerry, K4SAV


Rick Karlquist wrote:
> K4SAV wrote:
>   
>> I wouldn't recommend using the SteppIR elements as a capacity hat.  The
>> elements are insulated from the boom and most of them won't add a lot a
>> capacity.  The driven element has a 2 to 1 balun.  It also does a choke
>> function. The primary to secondary capacitance of that balun will
>> conduct some current and cause some dissipation.  The balun is unlikely
>> to have a high impedance on 160 meters.  It will also have a lot a
>> voltage across it.  I have not heard of anyone reporting a destroyed
>> balun, and I have heard of some people using the SteppIR elements for
>>     
>
> I don't agree with "a 2 to 1 balun ... also does a choke function".
> First of all, the impedance ratio is 9 to 4, and the turns ratio is
> 3 to 2.  Second, all "current baluns" or "common mode chokes" are 1:1.
> I have never seen one that is not.  I spent a lot of time analyzing the
> balun in my MonstIR and characterizing it on a network analyzer.
> IIRC, the balun is of the "voltage balun" type with a center tap connected
> at least to the outer conductor of the coax, if not the boom.  If you
> simply connect the outer conductor to the boom, near the balun, you should
> be OK.  You could probably get away with bonding the coax outer conductor
> to the tower near ground level in many cases.  You do need to do something
> to keep RF off the control cable of the SteppIR, but this problem
> exists whether or not you extend the elements to use as a capacitive
> hat.  If this is wrong, somebody correct me.
>
> Rick N6RK
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