Re: Notes on Terry's observations
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.
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>
> 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:
>A nice graph is at:
>The peaks of current match the harmonic voltage maximums from yesterday.
>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
>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!!!
>>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
>>Hope this info helps you out with your experiments.