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Re: Calculating secondary resonance of bipolar coils



Original poster: "Kurt Schraner by way of Terry Fritz <twftesla-at-uswest-dot-net>" <k.schraner-at-datacomm.ch>

Hi Gavin, Terry, ..bipolar-TC interested,

by good luck, I have a (-little big-)bipolar-secondary WITH a
centertap. My measurements and calculations support Terry's good
guess, about a center-plane, taking the function of a ground
plane, by reason of symmetry. The data of my coil are as follows:

diameter            16.33 cm     6.429"
winding length      140.1 cm    55.157"
number of turns     1950 (estimated by part count, not counted
full)
wire bare           0.64 mm
wire insulated      0.69 mm
space between turns 0.028 mm
inductance          67.7 mH (whole coil, measured by LCR meter)
inductance          32.42 mH (half coil, measured by LCR meter)
inductance          32.11 mH (half coil, measured by LCR meter)

The resonant frequency mesurements of the coil:

		Measurements 24.8.00 / Sk					
		Quarter-Wave-Coil Tests	
        Topload:        bare coil       Finn's 60/16.5cm
                                        12.5cm above sec.	
fo              kHz     147.700 147.700 102.630 102.614	        
70%, f -        kHz     147.251 147.268 102.085 102.055	
70%, f+         kHz     148.182 148.145 103.133 103.132
Bw. Df	        kHz     0.93    0.88    1.05    1.08
Q=XL/Rv	                159     168     98      95	
Rv              Ohm     396     373     446     458	
                        Harmonics		    
                        fhx     fhx/fo  fhx     fhx/fo
3rd             kHz     382.45  2.59    331.09  3.23
5th		kHz     558.42  3.78    523.06  5.10
7th		kHz     709.28  4.80    682.95  6.65
9th		kHz                     823.79  8.03		
11th		kHz                     950.66  9.26
	
		Instruments:					
		Siemens Level Oscillator W2087 (0.2...1620kHz)					
		Tektronix 7623 Oscilloscope					
		HP 5216A Electronic Counter ( up to 12.5MHz )				

- more data available -
	
  Half-Wave-Coil Tests !	
center tap, bare coil		
vertical        horizontal
267.785	        261.623
266.320	        259.970
fo second       263.080
test,above!     3.11
Q=XL/Rv	         84
R               661 Ohm
                Harmonics	
                fhx		
                654.13	
                928.27	
                1177.77	

Hope the tab's will not behave too badly on the posting!
I did a comparison of results from E-Tesla6, entering half of the
secondary, and got the following results:

fo = 268.8 kHz , Cself = 10.4 pF, by E-Tesla6, which compares
well to 
fo = 267.8 kHz measured (vertical position) or
fo = 261.6 kHz measured (horizontal position) of the coil.

I "think", even the design of a bipolar-coil, is easily done by
applying some of the standard TC-design tools Wintesla, Ed
Sondermans Excel-Spreadsheet or perhaps my own, to be downloaded
under:

HTTP://home.datacomm.ch/k.schraner/LongTC_Bipolar.zip

...only entering just half of the secondary coil, instead of the
whole bipolar secondary.

The remaining problems are: Good HV-end termination of the
bipolar coil (Construction? calculation? - probably by
before-mentioned methods), and coupling-factor calculation, which
can probably be done by Dr.Mark Rzeszotarskys MandK or Paul
Nichols's ACMI. While coupling is easier to trim, with a
quarterwave-TC, the one for a bipolar has to "stand" from
beginning, because there is no adjustment by way of positioning
the primary.

My own bipolar, yet needs to prove, what i believe, is nice to do
with it  ;^)).

Cheers, Kurt Schraner









	
	





Tesla list wrote:
> 
> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
> 
> Hi Gavin,
> 
>         I didn't quite know what to say but since no one else did either,
I'll
> give you my guess anyway.  You can use E-Tesla6 to calculate half the coil
> assuming the center plane of the coil is a ground plane.  Since a bipolar
would
> be half wave, I would guess the Fo frequency would be the same.  So, if
you run
> half the bipolar, I think it will give you the right Fo frequency.  I
think...
> 
> There are also supports and such that are going to mess with the external
> fields a bit too but I think it will be pretty close.
> 
> http://hot-streamer-dot-com/TeslaCoils/Programs/Programs.htm
> 
> When you ask a good question like this and no one answers, you know you have
> asked a good question ;-)))
> 
> Cheers,
> 
>         Terry
> 
> At 03:24 PM 1/4/2001 +0000, you wrote:
> >
> > Hi all,
> > I sent a mail to the list a couple of days ago regarding secondary bipolar
> > coil resonance calculations. As there has not yet been a reply, I thought I
> > should elaborate on the question I originally asked.
> > Most TCs are of the up-right quarter wave resonant type, topped with a top
> > load such as a torroid. I have recently wound a secondary more suited
for use
> > as a bipolar or half wave resonant secondary. The primary is positioned in
> > the middle of this secondary coil; and the there will be no earth
connection
> > at the mid point of the secondary.
> > Now, I know that it possible to calculate the resonant frequency of a
quarter
> > wave coil using medhurst and the standard LC resonance formula. It is also
> > possible to treat the secondary as a Tx line by determining the wave
velocity
> > from the coil inductance and capacitance per unit length. Medhurst, I
> > believe, was derived from empirical measurement, while the Tx-line method
> > relies on modelling. Either way, it seems that these methods do not
work when
> > considering half-wave resonators, the frequencies tend to be much greater
> > than, say, the medhurst calculation. So, has there been found a method of
> > calculating the half-wave resonance of a coil?
> >
> > Thank you in advance for your help.
> >
> > Gavin