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Re: Sphere/Toroid Comparison Chart
Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>
Hi Bart,
There is no question that the variation can go way beyond
20%. If the toroid is small enough relative to the resonator, the
change can approach 100% - i.e. it might as well not be there at all.
Pointless for operation but does make a point of its own.
Regards,
malcolm
On 8 May 01, at 22:52, Tesla list wrote:
> Original poster: "Barton B. Anderson by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>
>
> John, Terry, All,
>
> I've tested my two toroids and my measurements "do not" agree with
> less than 20% reduction of Ctop. See below:
>
> Tesla list wrote:
> >
> > Original poster: "John H. Couture by way of Terry Fritz
> > <twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net>
> >
> > Terry -
> >
> > I entered your coil's data into the JHCTES Ver 3.2 program to see
> > what it comes up with for a toroid. To get the 87.66 Khz the program
> > came up with 29 pf for the capacitance. This is about 12% less than
> > the graph shows (space 33 pf) for an 8 x 30 toroid. On my web site I
> > mention that the graph capacitance would be reduced about 20% when
> > placed on the TC secondary. It appears this may be too high a
> > percentage. We will have to wait until more data is obtained.
>
> I've been doing some toroid Fr tests the last couple weeks.
>
> Purpose: To measure the change in Fr vs. calc'd with two different
> toroid dimensions and also to check Ctop against Bert Pool's equations
> when C is placed on the secondary.
>
> Method: Frequency meter (0.1% accuracy at these frequency's) using
> Terry's TC Tuner. The secondary is set upon a pvc pipe stand (no
> primary). Toroids are lowered via pulley arrangement to measured
> distances. Tuner connects between bottom sec. winding and RF ground.
> Tuner dial is "finely" turned to acquire Fr indicated by led
> brightness. Tuner is measured with Frequency meter.
>
> This may sound a bit odd, but the tuner measurement is within 1kHz of
> measurements taken via oscope and loop antenna (running) and I checked
> it against E-Tesla6 (of who's Fr accuracy was less than 1kHz), so the
> method "is" working. The tuner acts as a device that captures the Fr.
> Every coiler should build one of these (it's so simple). Great job
> Terry!
>
> Toroids are precise measurements via circumference measurements:
> Toroid No. 1 = 7.7" x 32" at a calc of 35.2pF. Toroid No. 2 = 6.5" x
> 37.9" at a calc of 39.2pF. Secondary: 12.75" x 43.25".
>
> Toroid No. 1 (7.7" x 32")
> Level CalcFr MeasFr CalcC MeasC
> (inch) (kHz) (kHz) (pF) (pF)
>
> -1 76.8 88.8 35.2 21.0
> 0 76.8 88.4 35.2 21.4
> 2 76.8 87.8 35.2 22.5
> 3 76.8 87.6 35.2 22.1
> 4 76.8 87.0 35.2 22.7
> 6 76.8 86.8 35.2 22.9
> 8 76.8 85.9 35.2 23.9
> 10 76.8 84.7 35.2 25.2
>
> Toroid No. 2 (6.5" x 37.9")
> Level CalcFr MeasFr CalcC MeasC
> (inch) (kHz) (kHz) (pF) (pF)
>
> -1 74.2 82.8 39.2 27.3
> 0 74.2 82.6 39.2 27.6
> 2 74.2 82.2 39.2 28.0
> 3 74.2 81.8 39.2 28.6
> 4 74.2 81.3 39.2 29.2
> 6 74.2 81.1 39.2 29.4
> 8 74.2 80.6 39.2 30.0
> 10 74.2 79.7 39.2 31.2
>
> With Toroid No.1 data, the Fr ranges from 15.6% to 10.3% (closer to
> calculated Fr as toroid height is raised). Ctop for the toriod ranges
> from 40.3% to 28.3%! That's a affect (possibly due to large coil?).
>
> With Toroid No.2 data, the Fr ranges from 11.6% to 7.4%. Ctop for the
> toroid ranged from 30.4% to 20.4%.
>
> Other than the obvious (reacts as one would expect) height changes,
> something here does standout:
>
> Toroid No.1 is larger in cord diam. and smaller in outer diam. Thus,
> Toroid No.2 is "physically" farther away from the secondary and
> therefore less affected. Both toroids calc'd capacitances are similar,
> but toriod "proximity in relation to the secondary" appears to play a
> major roll in both Fr and Ctop change.
>
> I don't see a standard percent value we can throw to this (although
> anything is better than nothing). I know my secondary is on the large
> side and might be why my values for Ctop vary far more than 20%.
>
> If you have a huge cord size that is "suppose" to have a large Ctop
> value, you may be better off with a smaller cord size at a wider
> diameter (not because of the Ctop value, but due to the toroids
> proximity to the secondary).
>
> BTW, I also mounted the toriods on top of each other at 3" and 14"
> distances. By using 50% of each and applying these values to Bert
> Pools standard toroid equation (as d1 and d2), the accuracy was
> amazing (3% to 0.6% from measured). I also swapped toroids (who was on
> top) and there was very little change (I didn't expect that).
>
> BTW, the above data's toroid height was measured from top secondary
> winding to bottom plane of toroid. This of course was adjusted for
> center of toroid when using E-Tesla 6. BTW, at a hieght of 0 on the
> 7.7 x 32 toroid (or 3.85" for E-Tesla 6), I measured 88.4kHz and
> E-Tesla 6 predicted 88.49kHz. Pretty good program and Tuner!
>
> For E-Tesla 6, wall distance is used, but often times there are
> objects around that can affect Fr including my own body. One wall was
> at 80" and the other 3 were more than double that. I used the nearest
> wall at 80". Amazing program! BTW, ceiling height is 120", and I did
> "not" include a primary in the program (0 for all primary inputs -
> worked perfectly and was how I measured the coil). The primary should
> change results and then possibly Ctop would be in the 20% range or
> less. Maybe that is the next test.
>
> There is a proximity relationship here between toroid and secondary. I
> can't conclude much until a smaller coil is tested with these same
> toroids and test parameters (time to wind a 6" diameter coil).
>
> Just thoguht I'd share my results. Any thoughts from the list?
>
> Take care,
> Bart A.
>
>
>