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Quarter Wave Calculations, HELP!!!
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From: Andrew Chin [SMTP:chinny-at-ozemail-dot-com.au]
Sent: Friday, April 17, 1998 11:13 AM
To: 'Tesla List'
Subject: RE: Quarter Wave Calculations, HELP!!!
Sorry bout the carriage return. The word wrap gives
me the impression that it will send like that. Oh well.
Could you please tell me Wheeler's L formula? I already
know Medhurst's C formula.
I missed that point about the correct topload bit in my
explanation. So did I miss something in my reasoning?
I myself thought that this formula was way too simple but
I had no other way to prove it other than plugging values
into various Tesla Coil design programs. By doing so I
found that this method was fine.
With that formula confirmed, I then used the formula
F = 1/[2pisqrt(LC)]
Where the inductance of a single layer air core coil is
calculated using
L = N^2.r^2/[254(0.9r+l)]
Where L = inductance in mH
N = number of turns
l = coil length in mm
r = coil radius in mm
Solving for C would give me the total capacitance of the
secondary circuit required for resonance. So I used
Medhurst's C equation to find the self C of the coil. I
subtracted this from the total C and this got me the required
C for the top load.
Now all these were confirmed using other values plugged
into other design programs and gave me the same answers
(within 3 decimals.)
Could I have made a fluke?
PS I hope this time the hard returns made it in.
-----Original Message-----
From: Tesla List [SMTP:tesla-at-pupman-dot-com]
Sent: Friday, April 17, 1998 1:57 PM
To: 'Tesla List'
Subject: Quarter Wave Calculations, HELP!!!
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From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Thursday, April 16, 1998 2:38 PM
To: Tesla List
Subject: Re: Quarter Wave Calculations, HELP!!!
Hi Andrew,
First off, would you please insert the odd carriage
return. Ireceived your message truncated to a single line of ???
characters.
> From: Andrew Chin [SMTP:chinny-at-ozemail-dot-com.au]
> Sent: Wednesday, April 15, 1998 2:22 PM
> To: 'Tesla List'
> Subject: RE: Quarter Wave Calculations, HELP!!!
>
> I simply used a physics formula Frequency = Speed of light /
> Wavelength. In the case of a quarter wavelength tesla coil, the
> wavelength in this case would be 4 times the length of wire used
> to wind
The length of wire won't correspond with the coil self-F like that
i.e. a bare resonator will never resonate at a frequency such that
the wire is 1/4 wavelength long in it. You can do it by adding the
correct amount of Ctop but I haven't yet seen any good reason to do
so (other than providing some top energy storage). If you don't
believe me, measure all of your resonators without a topload. Just
use Wheeler's L formula and Medhurst's C formula to predict your
coil's frequency.
Malcolm