Cecil Moore wrote:
Roy Lewallen wrote:

So now you're saying that any coil at the base of a short vertical
antenna, regardless of its value, will have equal currents at the
input and output?


No, I didn't say that. I wish you would read what I say. If the coil is
a low reactance (not many degrees) and the current maximum point is inside
the coil, the two currents will tend to be equal.

I did read what you said. You said that it wouldn't exhibit a phase
shift if placed at a current maximum. The current at the base of a short
vertical antenna is at its maximum there. So now if you're saying that
it *won't* exhibit a phase shift if placed at the base of a short
antenna, let's try this. Suppose I remount my antenna to eliminate the
shunting effect of the mounting, and do my measurements at 3.8 MHz as
before. Suppose the base input Z is, say, 35 -j380. You choose any
inductor value you'd like, that will best illustrate your method, and
tell me what output to input current ratio to expect.

Ok, suppose I make the measurement at, say, 10 MHz, where the coil is
no longer at the current maximum. Tell you what. I'll set up a 33 foot
wire vertical, to eliminate the difficulty of the mounting
arrangement. I'll furnish you the base impedance at 10 MHz, and even
let you choose the inductor value. Be sure and choose a value that
will clearly illustrate your point. Using the fine education you
received from Balanis et al, calculate the current into and out of the
inductor (phase and magnitude), and I'll set it up and measure it.
Since it is a fair amount of work on my part, though, I'd like to do a
dry run first, using, say, the base impedance predicted by EZNEC.
Then, after you've shown us how you make the calculations, I'll build
the antenna and do the measurement. I'd hate to go to the considerable
trouble of setting it up and find that you somehow aren't able to do
the calculation.


I can't do the calculation because I don't know the attenuation factor.

What "attenuation factor" is it you need? Is it something that can be
measured? If not, how about an equation or prediction with the
"attenuation factor" as a variable? We can estimate a probable range of
values, then see if the measurement results are within them.

Do you think my inability to do the calculation proves anything about
what's happening in reality at the antenna? You guys need to turn loose
of the concept that what happens or doesn't happen on a piece of paper
dictates reality.

I hope to demonstrate what constitutes reality by theoretical analysis
and by measurement. Where I come from, that counts much more than
arm-waving, insulting, and vague explanations. Ultimately, each of the
readers of these exchanges will decide what to believe, and I'm sure you
will have convinced some.

I can describe a base-loaded configuration that will demonstrate the
principle. Take a 75m bugcatcher coil, one of the 6"x6" models, and
choose a stinger that resonants the antenna in the 75m-80m band. Then
measure the in and out currents at a frequency a little below resonance.

I have no disagreement that a "bugcatcher" coil, or any coil of
physically significant size, will exhibit a phase shift and magnitude
change of current from one end to the other. Where we disagree is that
you believe that a physically very small inductor will also exhibit
this. I don't. I'm proposing a test which will show, with reasonable
certainty, which viewpoint is correct. I fully expect every test I make
to bring forth a flurry of objections. So I'm giving you the opportunity
to choose the inductor which will best illustrate your point of view. I
want to limit the parameters of the test to conditions I think I can
measure with reasonable accuracy. With the equipment I've got, that
pretty much limits me to doing measurements at the antenna base. But I
think (although I'm still not sure) that you're now saying that there
should be a substantial current difference between the input and output
of a small inductor at the base of an antenna, if the antenna and
inductor are properly chosen. So, you choose. And if you won't make the
measurement, I will.

Roy Lewallen, W7EL