Topband: tower resonance

[Tom Rauch]

> I would like some advice on how to measure the resonant frequencies of
> a grounded tower with HF arrays, guys, etc, etc, on it.
> 
> This is related to the antenna interaction questions discussed
> earlier.
> 
> 73, Rudy N6LF

I generally use a field strength meter with a built-in loop antenna. 
I do a skeleton proof whenever anything is changed to be sure my 
vertical patterns are OK.

It is possible to find inexpensive selective level meters available 
that cover 160 meters and higher, and build a small sampling loop for 
them.

Another useful tool, if you like to climb, is a sensitive current 
meter like the one MFJ sells. *IF* that meter is calibrated on the 
fixture I sent them, it should be within 10%. It reads currents from 
a few amperes down to a few dozen mA.

To measure current in a tower, you would have to build a sampling 
loop loop that is wound through the snap-on core of that meter, and 
move it up and down the tower.......unless you know where the current 
maxima will be.  

You can calibrate any small loop with any detector by placing it near 
a conductor carrying a known amount of RF current, and observing the  
reading.73, Tom W8JI
W8JI@contesting.com