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Re: Notes on Terry's observations

Hi DC,

	The signal generator has less than 1 ohm output Z at the frequencies
involved.  It has a 50mA current limit and if it clips, the signal is
obviously distorted but I never get close to that limit.  The generator is
based on the MAX038 chip and has excellent output characteristics.  Easy
for the do it yourselfer to wire up...  Malcolm clued me onto this great
chip a few years ago.

I placed a 50 ohm (49.816) resistor in series with the generator output and
connected the HP34401A across the resistor.  In this way, I can measure in
input resistance over the meter's rated 300kHz range.  The meter is "pretty
accurate" to ~1000kHz so I went up to that frequency for my new test. The
maximum current drawn was 1mA for the peak so the signal generator is not
being loaded much and the 50 ohm resistor should be negligible.  The
current peaks are at:

Terminal	Bare

84.63kHz	141.7Khz
310.0		342.5
475.7		496.5
629.3

A nice graph is at:

	http://users.better-dot-org/tfritz/Current.jpg

The peaks of current match the harmonic voltage maximums from yesterday.

Terminal	Bare

82.6kHz	137Khz
310.2		341.0
477.9		504.1
636.6


The multiple frequencies of 84 and 142 are:
1   2   3   4   5   6   7   8   9
84  168 252 336 420 504 588 672 756
142 284 426 568

So it looks like the input current is still tracking as a 1 2 4 6
progression of harmonics when one looks at the voltage graphs that appear
to be correct.  Noting that the harmonics above the fundamental tend to be
changed a little by the "not quite a sine wave" distortion in the terminal
case and the "tails" in the voltage distribution in the bare coil case as
shown at:

	http://users.better-dot-org/tfritz/VoltDist.jpg
	http://users.better-dot-org/tfritz/VoltDistBare.jpg

So the results as taken by the little antenna, the measured input current,
and the peak locations all match. The harmonics really do appear to be a 1
2 4 6 progression.  Of course, the problem is the frequencies are not what
we would expect (84 168 336 504).  I suspect these harmonics are setting up
a self capacitance in each voltage peak section along the coil.  This
capacitance is smaller than usual and is accounting for the higher
frequencies.  I "think" I can put real numbers, equations, and calculations
behind all that.  As far as what this means to the transmission line
theories, I'll leave that to those in the other camp ;-)

I do not think turn to turn capacitance is a factor at the frequenices we
work at.  I think the distributed capacitance is the same regardless of the
coil turns, pitch, guage, etc.  I will go with the paper by Medhurst on all
that.  Of course, a terminal added to the space surrounding the coil will
affect the capacitance greatly which is what E-Tesla3 calcualtes (that
program may need some looking at ;-)).

My terminal is giant but it isn't real small either.  The harmonics from
bare coil to coil with terminal seem about the same to me...

Thanks for suggesting the current measurements!  They are very interesting
and add much to all this.  Seems to be more questions than answers right at
the moment.  But we like it that way!!!

Cheers,

	Terry



>Hi Terry:
> 
>Some signal generators are altered by the circuit under test especially at 
>resonance as the current drawn increases sharply.  Assuiming you were using 
>a good low impedance instrument as you indicated the readings are valid.
> 
>A 1/2 wave resonators peaks I (current) at resonance while a 1/4 waves 
>resonator peaks voltage at resonance.  The secondary coil acts like a 
>transmission line if the upper terminal is small to medium size.  
> 
>If you connect a sensitive current meter in series with your signal 
>generator as you take the measurements you will see the 1,3,5 multiples 
>peaking while the voltage peaks from your cell phone antenna are peaking at 
>1,2,4,6.  This is normal and to be expected.
> 
>The toroid reacts with the secondary distributed capacitance which is 
>comprised of the many small series capacitances between turns.  The 
>harmonics are supported by the turn to turn capacitances, ie, distributed 
>capacitances.  This effect is what produces all the multiple harmonics you 
>are observing.  If you connect a super huge top load capacitance you will 
>see only one fundamental with any multiple resonances produced attenuated 
>down by 10-20 dB, and, in effect, do not become part of the active secondary 
>circuit due to their attenuation.  This is why TC tuners should always use a 
>very large topload, ie, to prevent all the undesireable multiple harmonics 
>that cause strange effects which some experimenters call "racing sparks" 
>along the secondary coil.  Use a huge topload and "racing sparks" will 
>disappear altogether assuming the primary is in proper tune.  Racing sparks 
>are caused by too small topload and multiple series resonances with the 
>distributed capacities along the secondary inductor reacting with the 
>topload capacitance.
> 
>Hope this info helps you out with your experiments.
> 
>Dr. Resonance
> 
> 
> 
>