Re: Another obnoxious lumped theory supporting post ;-))

• To: tesla-at-pupman-dot-com
• Subject: Re: Another obnoxious lumped theory supporting post ;-))
• From: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Sun, 16 Apr 2000 17:19:33 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

HI all,
          I would like to mention a couple of things that might be of 
interest to people who are new (on the list) to this debate. One in 
particular might be of interest to a greater number.

     First thing - a clever chap named Ed Harris who was once on 
this list came up with a wirelength formula that really worked for 
predicting resonant frequency of a helix to within 5%. It is the only 
formula I know of (out of perhaps a dozen I've seen over the years) 
that did work. It incorporated third and fith powers in places if I 
remember rightly (the same sort of thing that is embodied in 
Medhurst's Cself formula). There were interesting equivalences in 
there.

      Second thing (this is for those who believe electricity spirals up 
a length of wire). I picked out one of my resonators at random and 
came up with the following (this is the same resonator I used in a 
working coil a couple of weeks ago):

Closewound with 0.56mm wire
Diameter = 4.8"
Winding Height = 21.8"
Turns = 914
Measured (and calculated) Inductance = 20.1mH
Capacitance (calculated using Medhurst's formula) = 9.4pF
Resonant frequency = 393.3kHz (measured but you can calculate it
from L and C to see how far off it is).

Now for the interesting bit:
- wirelength = 350m
If this was strung out as a vertical monopole, one would expect it to 
resonate in 1/4 wave mode at 214kHz-odd (you can do the calc)
Note that the bare resonant frequency is considerably higher than 
this. 
       My conclusion : winding the wire up like this causes a drop in 
Cdistr that is not met by the rise in L due to mutual coupling between 
turns since k is << 1 for the resonator as a whole. So does 
electricity really travel up the wire faster than it can if the wire is 
strung out as a long length?  This is not a random result - it applies 
to each and every resonator of this type ever built. I tweaked to this 
fact five years ago. I wonder what the heck people are talking about 
when they speak of the need to "add top capacitance to bring the 
coil into 1/4 wave resonance".

Fwiw,
Malcolm

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