Re: Notes on Terry's observations

to: Terry

I believe the current readings will shed some more light on your work.

With all these small series capacitances some begin to also react with other
capacitances a few inches up or down the coil so it does get quite wierd to
predict perfect outcomes.

Sounds like you're having fun.


Dr. Resonance

-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Saturday, August 28, 1999 4:06 PM
Subject: Re: Notes on Terry's observations

>Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>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
>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
>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!!!
> 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
>>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
>>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
>>circuit due to their attenuation.  This is why TC tuners should always use
>>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
>>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