Today's project was to construct and measure a more idealized antenna.

The antenna is 33 feet high, made of #16 insulated wire. I put out 23
radials on the surface of the wet ground. Radials were of various
lengths, most about 30 feet long. The feedpoint impedance of the
antenna, measured with a GR bridge, was 15.8 - j437 ohms at 3.8 MHz.
Allowing 3% lengthening effect for insulation, EZNEC says a lossless
vertical of that height and diameter should have an input Z of 7.5 -
j478. 8.3 ohms loss resistance is reasonable for that number of radials,
and the somewhat lower than predicted reactance is likely due to the
fact that the radial wires were grouped together as they came up a few
inches to the antenna base, and not immediately coming in contact with
the ground. That would add a bit of inductive reactance.

I wound an inductor on a T-106-6 core as before, but with more turns,
for a measured Z of 1.3 + j387 ohms. After putting it in series with the
antenna at the base, the base impedance measured 17.1 - j54 ohms. This
is only 4 ohms from the expected reactance, and spot on the expected
resistance, so measurements are consistent.

Analyzing verticals with EZNEC, made from #16 wire at 3.8 MHz, shows that:

-- An antenna 63.2' high is resonant.
-- An antenna 35.9' high has a feedpoint reactance of -j437 ohms.
-- An antenna 59.35' high has a feepoint reactance of -j54 ohms.

With a resonant height of 63.2', you could say that 63.2' is "90
electrical degrees" as far as the antenna is concerned. So you might say
that my inductor has "replaced 33.4 electrical degrees" of the antenna.

Using Yuri's cosine rule, we should then expect the inductor output
current to be cos(33.4 deg) times the input current, or 16.5% less.
Also, we should expect to see those 33 degrees of "replaced antenna" as
phase shift from the input to the output of the inductor. That is, the
current change from the input to output of the inductor is the same as
it would be for the portion of the antenna it "replaces". (I think Jim
Kelley subscribes to this theory also, but I'm not sure.)

In contrast, conventional electrical circuit theory predicts no current
difference between the input and output for a physically very small
inductor with no radiation or stray coupling. I saw about 3% in the
previous measurement, which I believe can be attributed to stray
capacitance. So I predicted that we should see about twice that amount
with the higher valued inductor used for this experiment (387 vs 192
ohms reactance). I didn't see any measurable phase shift between input
and output before, so I didn't expect to see it this time.

So for this test, there's quite a difference in predictions for
output:input current --

**Yuri's method predicts a reduction of output current magnitude of
16.5% and a phase shift of 33 degrees.

**I predict around 6% magnitude reduction (due to stray C) and no
measurable phase shift (less than 2 or 3 degrees).

I have very high confidence that my measurements are good enough to
resolve the difference between these two possibilities.

Would anyone care to comment before I post the measurement results? And,
Yuri, please correct me if I've misinterpreted your theory.

Roy Lewallen, W7EL