Jim Lux said:
"I would guess that the measurement uncertainty (and modeling
uncertainty) is sufficiently large that the modeled and measured are the
same."
Jim, inductance critically depends on coil diameter. But I only have a
tape measure, nothing more sophisticated. In addition, the diameter
differed for two measurements 90 degrees apart on the coil. Instead of
averaging them as I should have (or slightly squashing the coil), I took
the easy way out and just used the nearest scale measurement. Later I
thought about going back and remeasuring more carefully, but to me a
decision like that after seeing the results has a whiff of drylabbing
even though it's made in the spirit of better accuracy. So I decided to
let the measurements stand.
Highly variable Q with hand placement at 3.7 MHz was not a surprise. But
I was surprised to see no effect at all later at 1.8 MHz.
I forgot to mention that calculated Q peaks at 876 at 7 MHz. I couldn't
measure that high because the meter's variable capacitor ran out of
adjustment range. But I believe the calculated number, +/- 10%.
I originally intended to do a second measurement with the coil elevated
about 3 feet above the meter to greatly reduce the effects of the
enclosure. Then I'd use the software I wrote to undo the effect of the
long transmission line to obtain results for the coil with no leads. But
I found the stiff #10 wire so difficult to work with even for short
leads that I decided to forego the second measurement. The 4342A has
fussy terminals and it's very hard to get the bends just right to make
solid connections. The 3.7 MHz Q measurement is not that far from
calculated anyway although it did depend on magic hand placement.
The main objective was to see if a QCoil coil had reasonable Q. It
certainly does.
Brian
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