# Re: 1/4 wave theory/cite the variance?

```Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 2/17/02 11:09:33 AM Eastern Standard Time, tesla-at-pupman-dot-com
writes:

>
> All,
> One of the reasons that i wound the 3000 turn coil was to see if i could
> notice any effects of winding a coil "over" the 1\4 wave of the wire.
>   Using wintesla i wound the 8.75" coilform with roughly 7100' of 28g
> wire to a length of 42.5", This using my 6" x 24" dtc-at-32.1pf topload
> gives a 1\4 wave of 6843', 257' of wire over.
> I wondered if the windings at the turning point of the wave would get
> hot or anything, well it didn't.
> It is entirely possible that the toroid not being totally smooth has
> effected this "rough" experiment? I had planned on removing wire until
> i could get right on the 1\4 wave, but it became a factor in the tssp so
> i never tried it.
>

Hi Marc,
Glad to see real world measurements occurring. As to this particular
experiment: your overwind of 257' out of 6843' is a 3.76% increase. If 1/4 wave
theory is correct, then peak top load voltage misses the ideal by
sin(90+-3.76%)= sin(93.38deg)= 0.9983 or 0.27% lower. All else being equal, it
seems that this should result in a decrease of power to streamers on the order
of 0.6%. using the rule of thumb: Length1=1.7sqrt(P), and
length2=1.7(sqrt(.994P)). At 5KVA the difference would be 120.21" - 119.85"= or
~3/8" average difference on 10ft streamers. Given the inherent variations in
Tesla coil performance with changes in temperature, humidity, air pressure,
line power fluctuations, surrounding objects (including observer) it seems like
it will take an extremely large number (100s) of careful observations to detect
such a small variation.

1. Would someone please cross check the math and reasoning of the above?

2. Does anyone on the list have the equipment to accurately detect such tiny
differences in TC output voltage or power?

3. If 1/4-wave theory and the above reasoning is correct, then even a 5%
decrease in output power would require ~2.5% change in voltage and
Arcsin(.975)~78deg. This corresponds to a difference in your particular coil
length of 12/90*6843 = 912ft to show even a 5% variation.

As Prof. Yardley Beers, guru of error theory, late of NYU, once said,
"When measuring with a wooden yardstick, don't be surprised if an elephant with
a flea on his back seems to be exactly the same height as with the flea
removed. Nevertheless, the flea would object to the conclusion that this
established his nonexistence, though it does, for the sake of
elephant-measuring, establish his insignificance"  ;-)

Good luck,
Matt D.
G3-1085

```