On Tue, 28 Nov 2006 23:06:21 -0500, John Ferrell
wrote:

On Tue, 28 Nov 2006 22:25:45 GMT, Owen Duffy wrote:

On Tue, 28 Nov 2006 16:24:07 -0500, John Ferrell
wrote:


What I expected to see was some thing resonant between 6-8 mhz with a
lot of reactance and who knows resistance. It did not happen....

I don't really understand that, what is resonance, and why would there
then be lots of reactance?

Owen
I expected a dip in the swr at the 1/4 wave length but not a 50 ohm
match.

John,

Your terminology has me confused.

When you say you expect to see resonance between 6-8MHz, I understand
resonance to mean zero reactance at that frequency. Then you tell us
you expect to see lots of reactance. They are inconsistent.

Then you tell me that you expect to see a dip in SWR at the 1/4 wave
length. I am guessing, but I think you probably mean the frequency
where the vertical is a quarter wavelength long electrically.

If you drive the vertical at the base in series, you would expect to
observe resonance (ie no reactance) somewhere around the quarter wave
frequency.

If you shunt feed it further up, the shunt feeding arrangement acts as
an impedance transformer, and it is unlikely that you will see zero
reactance (ie resonance) at the same frequency as if you series fed
the vertical at the base. A feature of shunt feeding typically is that
it is reactive, and you have to tune out the reactance, adjusting the
tap point up or down to get the desired feed impedance.

Owen
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