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Re: Wire length,resonance, and Q (fwd)
---------- Forwarded message ----------
Date: Tue, 12 May 1998 17:55:47 MYT
From: Sulaiman Abdullah <sulabd-at-hotmail-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re: Wire length,resonance, and Q
>To: "'Tesla List'" <tesla-at-pupman-dot-com>
>Subject: Wire length,resonance, and Q
>Date: Tue, 12 May 1998 01:07:47 -0500
>From: Tesla List <tesla-at-pupman-dot-com>
>
>
>----------
>From: bmack [SMTP:bmack-at-frontiernet-dot-net]
>Sent: Monday, May 11, 1998 9:43 PM
>To: tesla list
>Subject: Wire length,resonance, and Q
>
>To all,
>
>When Dr. Tesla made initial coil designs, he often resorted to quarter
>wave length calculations as a guide. My early impressons of this was
>that it was the upper boundry for the physical length of wire that
could
>be used. Since, however I found that this is not neccessarily the
case.
>
>The most intriguing thing is the cases where the coil resonates at
>frequency HIGHER than the wire length alone indicates! Malcolm made
>a passing refence to this in one of his recent posts as well.
Preliminary
>quick experiments indicate that the coil geometry has alot to do with
it's
>ultimate resonant frequency apart from the length of the wire. Really
>bizzare things happen when the aspect ratio is below 0.1.
>
>According to conventional physics, (let me know if I missed something)
>a charge and it's attendant feilds will propagate faster in a straight
>wire
>than in a coil. It follows that the coil should always resonate lower
than
>the wire since the velocity is less than the speed of light.
>
>Why then, do long space wound coils resonate at a frequency higher
>than expected? This has nothing to do with the LC ratio either. I would
>expect that no matter what gain or reduction of L vs C for a given
>geometry, they should always result in a frequecy lower than that of
>a straight wire. Whats going on here???
>
>Before I go and re-invent the wheel, does anyone have an explaination
>and/or experimental data on this?
>
>Curious in NY
>Jim McVey
>
>
My $0.02,
The 'resonant' frequency of a straight wire is when the electrical
length (adjusted for velocity less than light-speed) equals
one quarter wavelength. (No controversy here)
Our coils have TWO resonant frequencies; one is equivalent to the
straight wire case, quarter-wavelength; the other is determined
by self inductance and capacitance which for typical coils WILL
be at a higher frequency than the quarter wavelength frequency.
Ideally we add capacitance to bring the LC resonance down to the
same frequency as the quarter wavelength frequency to ensure
optimal performance, that is no standing-wave-type voltage peaks
before the top-load.
I've noted that many coilers operate even below this frequency to
get big fat discharges, no problem.
I've also seen many posts reporting discharges part-way up the
secondary, indicating insufficient top capacitance.
The L and C values WILL determine the resonant frequency,
the quarter wavelength effects determine WHERE the peak voltages
appear along the length of the secondary.
SUMMARY Operate at or below the quarter wavelength frequency.
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