Ah,

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?

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.

Other predictions would be welcome, too, such as Yuri's, based on the
"missing antenna length" theory of inductor currents.

Better yet, you can do the measurement yourself. As you can see from the
picture I just posted to my web site, the measurement ain't exactly
rocket science. I don't have much time to burn, but still shook loose
enough to set it up. Anybody with a two channel scope, a soldering iron,
and a signal generator or transmitter can do just what I've done. You
can too.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

Can I conclude from this that if I were to make a coil with more or
less inductance, then I would see a current difference between the
ends of the coil?

So tell you what. If you'll pull out your equations and calculate the
expected current difference, I'll replace the coil with one of 100
ohms reactance and remeasure. How much current difference (magnitude
andd phase, of course) between the ends of a 100 ohm inductor at the
base of that same antenna?


I know you are not that naive, Roy. I have said many times over the past
few days that if you locate a coil at a current maximum point, the current
will be approximately equal at each end. So what did you do? You locate
your coil at a current maximum point and I assume your measurements proved
me to be correct. As long as you install the coil at the base of the
antenna, the currents are guaranteed to be close to equal as I have
said any number of times.

If you place the coil at a location where the slope of the current is
maximum and positive, the current through the coil will *INCREASE*.

If you place the coil at a location where the slope of the current is
maximum and negative, the current through the coil will decrease. This
is typical of center-loaded mobile HF antennas.

Incidentally, Kraus engages in some of your alleged "pseudo-analysis"
in his book. He clearly shows the current drop through loading coils.
He even says a coil can be used to shift the current by 180 degrees.
Come to think of it, my 440 MHz mobile antenna has a coil in the center
that shifts the current by 180 degrees yielding considerable gain
from those two phased elements.