Dave wrote in
news
Cecil Moore wrote:
Bill Turner wrote:

You restated what I said in much more detail, but what you have done
is expounded on the "what". I still don't know the "how" or the
"why".


The Smith Chart yields the "how". Please take the "why"
up with The Creator. :-)

Cecil --- you are begging the question!!

I reported that the addition of 3 or 4 inches above the coil produces
a much larger shift in frequency than adding the exact same length
below the coil [by almost a factor of 100:1]. That is empirical data.
It is real and measurable.

My question is one of Physics. I think everyone who reads this list
knows it happens. The real question is: Why?? Why the difference in
antenna resonant frequency?

Let me try. If you look at the antenna as a set of lumped circuit bits,
the lower mast portion is mostly just a wire with radiation losses. The
coil and stinger form a series resonant circuit back to ground, thus a
small change in either will result in a different resonant frequency.
The antenna only presents a low, resistive load, at resonance, so
changing the stinger length (thus varying the capacitance to ground)
changes the resonance rapidly. Changing the length of the high-current
lossy feeder pipe below the coil does little, though it will increase
efficiency if you make it as tall as possible.

--
Dave Oldridge+
ICQ 1800667