Cecil Moore wrote:
What was the indicator? What was the coupling device?

I have an assortment of toroids of various materials from Amidon. I'm
at work right now and I don't remember if I used 43 or F material.

How did you construct the coupling transformer? How did you make it
immune to electric fields?

On six meters, it would take a darned small probe and indicator to not
greatly perturb the system.

They are small toroids. I chose 6m because the dipole area was
physically small.

They may be small toroids, but what do they connect to? What is the
common mode impedance of the indicator at 50MHz?

If I was going to test something like this, I'd use a small indicator
hanging from the antenna and do it on a low frequency.

Please feel free to make that measurement. W7EL just reported that
EZNEC agrees with my phase measurements. So does Kraus.

You may not have been measuring anything like you think, in particular
voltage. Just because EZnec agrees with the phase measurements it
doesn't mean the current measurement was even remotely close to being
correct.

So, tell us about the probe and indicator.

Similar to the ones W7EL used. They were calibrated within one turn
of each other. The signals at the ends of the coax lines were calibrated
for equality in magnitude and phase. Magnitudes are a relative measurement
but phase was not. I ran the experiment two ways.

I you hung coaxial lines off a current transformer on a 6-meter dipole
down to some test instrument, you wasted a lot of time. There isn't any
possible way you measured an unperturbed system.

You'd better reconfigure as a monopole, and do it on a lower frequency.


One was Lissajous figures on my 100 MHz Leader. The other was putting
the two samples in opposite phase to each other, i.e. phasor subtraction.
For small angles, the angle is equal to the sine of the angle so the
addition
of two coherent sine waves yields an amplitude proportional to the phase
difference when the phase difference is small. The phase difference was
so small it was virtually undetectable.

I wouldn't trust that system at all.

Even with the equipment I have and having build hunderds of sampling
systems, I'd never attempt a measurement like you just made.

You brought a pair of long coaxial lines that are grounded at the far
end up to within an inch of the antenna, hung what amounts to being a
capacitor between the high voltage high impedance side of the antenna
to ground, and presumed to measure voltage and current on six meters!

You can get away with a toroid on 80 or 40 meters if the test gear and
lines are all near ground potential along with the point of the antenna
you are measuring, but it is really off the wall to assume you can hang
a toroid on a dipole past a loading coil, have that toroid connect to a
cable hanging in air down to some test gear, and not severely perturb
the system. Worse yet, the test was done on 50MHz!

I used a very small floating probe with NO earth path and the indicator
right on the probe. I had to do that to not perturb the system on 40
and 80 meters. I can't imagine trying to do what I did on six meters,
I'd have needed an entire metering system the size of a half-dollar or
smaller.

Making a measurement at the base of a vertical on a low frequency like
Roy did allows the person making the measurement to get away with lots
of things, but I can tell you right now I'd NEVER be able to measure
anything in a short mobile antenna if I ran cables up to the probes, in
particular if I made the test on six meters!

73 Tom