[TowerTalk] Measuring voltage along an element

[Jeff Carter]

I haven't ever really given it a lot of thought, but wouldn't this be an
Ohm's Law problem?

In other words, couldn't you use the characteristic impedance (Z0) of your
antenna and then get the voltages by Voltage=CurrentxImpedance?  I realize
there's a possibility that the impedance will vary at different points, and
the voltage will lead or lag, but it strikes me that this is a good way to
get at least a rough idea.

Jeff/KD4RBG

On Sun, Nov 8, 2009 at 12:42 AM, Denis Coolican <coolican at telus.net> wrote:

> Possibly someone can help.
>
> I am building/designing a 2 element 80m Yagi with elements that can be
> adjustable in length.  The elements will have a total length of 100 ft and
> as such I do have a loading coil of about 15 microhenries in each half of
> the element.  The coil and the element length adjustment mechanism is
> located at the center of the element.
>
> Since the elements are so long and are adjustable I have a triangular
> structure that goes out for 30 ft from the center to support each side of
> the elements. The structure will be at ground potential.  I realize that the
> voltage across the coil will be high for an air coil (about 3.5 KV at rated
> power levels).
> I can see what the magnitude of the currents are but I would like to be
> able to calculate or estimate what the voltage is between the element and
> the structure (ground) such that I can make sure I have the correct amount
> of insulation.
>
> I do not see anything in the handbooks on this subject.  I was wondering if
> anyone can help.
>
> Denis ve6aq with ve6fi
>
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