Ian White GM3SEK wrote:
Such probes are routinely used for RFI, RF hazards and screened-room
measurements, where connecting wires would disturb the fields or act as
pathways for RF leakage.

They do have a disadvantage that might be relevant to this discussion:
because the probe head has to be self-powered, and has to include some
kind of encoder and optical transmitter as well as the normal current
transformer, the battery and extra area of PC board will increase the
probe's self-capacitance.

There are two advantages to a fiberoptic coupled probe. One advantage
of fiber optic coupling from probes to indicator is the coupling leads
from sensor to indicating instument do not have a good direct path to
earth or equipment like conventional probes.

I actually built a form of this for one of the measurements Ceci
rejected.

http://www.w8ji.com/building_a_current_meter.htm

In this case the information, current, is conveyed by light through air
directly to my eye.

For the purposes of this discussion, however, the real advantage is
different. Since it is unlikely anyone disagreeing has a fiber-optic
coupled probe (the fiber optical cable simply replaces the wire between
the sensor and the indicator or sensor information processing system)
it is unlikely anyone can prove Cecil wrong.

This all seems logical to me, because Cecil has asked for measurements.
The pattern has been after he gets measurement results and finds they
disagree with his theory, he has to blame the difference on something.
The most logical thing any person can do when they repeatidly accept
results of measurements made by multiple people using multiple methods
is to come up with a measurement no one can make.

For example?

Most people understand a current transformer measures current. The
original debate was K3BU and W9UCW made a statement current is high
only in the first few turns of a loading inductor, and thus loading
inductor Q did not matter for efficiency of an antenna.

I proposed antenna losses were swamped out by ground losses in a
vehicle, and because of very high ground losses the effects of coil
resistance were diluted.

I measured the inductor and found as quite logically anyone would
expect that current ratio depended on the ratio of stray C from the
coil to load C at the open end of the coil. Yuri K3BU argued the coil
replaced a certain number of degrees electrical height, and I
disagreed. I said a 20-degree long antenna with a loading coil did NOT
have 70 degrees of antenna wound up in the coil.

Most people experienced in systems like this from an engineering
standpoint agreed with me. Somewhere about that time Cecil brought
reflected waves into the discussion.

After a series of "what happens if" Cecil wanted measurements. When
they were made, he and Yuri announced the measurements proved their
points. When the person making the measurements corrected those
misstatements and pointed out the measurements didn't support their
claims, the only logical course was to discredit the measurements and
ask for new ones.

When new measurements again disagreed with the concept of huge current
or phase delay of current that was tied to degrees the coil replaces,
the only course was to reject those measurements.

So here we are today, two or three years later, still trying to find a
measurement that will agree with what Cecil and Yuri proposed or for
another person of reasonable engineering experience to agree with the
notion the coil behaves as a coiled up antenna or transmission line
rather than behaving more like a lumped component in a small heavily
loaded mobile antenna.


Since dozens of hours of measurements acceptable to most people were
rejected, the only solution would be to require a measurement with
instrumentation no one has. This way Cecil can say no one can prove him
wrong, and that allows him to continue to demand others agree with him.

In my opinion, the real advantage of optically coupled probes in this
thread is no one is likely to have them.

73 Tom