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FW: 1/4 Wave, etc.
From: Dan Kline[SMTP:ntesla-at-ntesla.csd.sc.edu]
Reply To: ntesla-at-ntesla.csd.sc.edu
Sent: Friday, September 12, 1997 10:14 AM
To: tesla-at-pupman-dot-com
Subject: Re: 1/4 Wave, etc.
>From: Greg Leyh[SMTP:lod-at-pacbell-dot-net]
>Sent: Thursday, September 11, 1997 1:25 PM
>To: Tesla List
>Subject: Re: 1/4 Wave, etc.
>
>Alfred A. Skrocki wrote:
>
>
>> Hi Pete, a 1/4 wave coil is a coil such that the length of the wire
>> wrapped around the form is 1/4 the resonant frequency of the
>> finished coil.
>[snip]
>> BTW it is not as
>> easy to make a coil 1/4 wave length as it would seem! There are many
>> factors that alter the resonant frequency of the coil and these are
>> very difficult to account for before the coil is actualy wound, but
>> when it is achieved the results are usually spectacular! The most
>> important of these factors is the combined distributed capacitance of
>> the finished coil and it's top terminal.
>
>
>It does not seem that the sec wire length makes an appreciable
>difference in the performance of a standard TC.
>
>I have noticed in PSPICE that typical TC secondaries with even moderate
>top loads do not exhibit any significant standing wave behavior, but
>operate more as simple LC resonant circuits. The voltage profile for
>a normal TC along the sec is roughly linear, and only when the secondary
>becomes coarsely space-wound with no top load does the voltage profile
>start to bend into a quarter-sine.
>
>This explains why Richard Hull and others have discovered that more
>top load is better, with no discernable correlation between the
>operating frequency and the electrical length of the resonating coil.
>
>
>-GL
I know that above is true, but I think I remember someone posting once that
the ideal topload, for beginning experimentation at least, I guess, was
that topload which would lower the secondary's un-top-loaded resonant
frequency to 0.707 of what it is when unloaded.
For example: If the unloaded resonant frequency was 200kHz, then the ideal
top-load would lower the frequency to 141.4kHz, other parameters being
appropriate, of course.
Is this in error? It's not like I hold to that design or anything, but lots
of people like to have a starting point :)
Thanks,
Dan