Re: More Coupling...

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Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Paul, 

This post should clear up some discrepancies: 

This morning, I set up the coil and made measurements. Before I get to
that, I found my old post to the list regarding the measurements I made
back in March, and I thought K was too high and questioned the list about
it. The 2.59V at secondary was not 1.5" above but 1" below! (I kept the
data in Excel but not the s-p proximities). 

Today, instead of a hair dryer, I decided to use something else that would
have little variation for hopefully a more accurate reading. I happen to
have a 3000W resistor (3" x 24"). This allowed 13.47 Amps. The results are
"much" lower than previsous (March, 2000). Anyway, here's the data (view in
fixed width font): BTW, good calc on the secondary windings. It's 1,041
turns (you missed it by 2 turns). 

S-P (INCHES)    SEC. VOLTS      M         K 
------------    ----------    ------    ----- 
2.00 (above p     1.937        381.4    0.125 
1.75              2.009        395.6    0.129 
1.50              2.064        406.4    0.133 
1.25              2.116        416.7    0.136 
1.00              2.122        417.9    0.136 
0.75              2.214        436.0    0.142 
0.50              2.284        449.8    0.147 
0.25              2.334        459.6    0.150 
0.00              2.441        480.7    0.157 
- 0.25 (below p)  2.452        482.8    0.158 
- 0.50            2.529        498.0    0.163 
- 0.75            2.543        500.8    0.163 
- 1.00            2.621        516.1    0.168 
- 1.25            2.645        520.9    0.170 
- 1.50            2.756        542.7    0.177 
- 1.75            2.761        543.7    0.177 
- 2.00            2.843        559.8    0.183 

Well, that's it. When I was ready to measure, I expected similar results to
my previous measurement, but, that didn't happen? I went back out today and
played used the hair dryer to see if I could find the reason the readings
changed, but the readings calc'd out to similar K values as above. I think
these values are "lower" than you predict. I took my time and ensured
measurement readings and height changes were as exact as humanly possible.
If there is variation from step to step, it is very slight (used a
calbrated caliper). The meter used is a Fluke77 (calibrated). Even with
this precision, I noticed some values above changed slightly at times (odd
but true). This can be due to some movement horizontally (while moving the
primary up, possibly a slight movement to one side of the secondary more
than the other). Even this would be slight (by design, the secondary is
centered to the primary with maybe an 1/8" movement from side to side). 

In the March measurements, I doubt the hair dryer was inductively coupled
as the primary is approximately 30" above the floor and the hair dryer was
simply laying on the ground at least 5 feet away. The "only" difference I
can find is the spark gap assy is not inside the housing this time (which
the primary/secondary sits upon), but I can't see that as a cause of the
change. The cap/resistor/wire assy used for the secondary measurement is
the same as previously used (and I mean identical - never took it apart -
found it ready to go). No clue why the change, but today's measurements are
what they are. I feel fairly certain of these. 

Take care, 
Bart