Re: Magnifiers

On Mon, 19 Jul 1999 17:17:47 -0600, Tesla List wrote:
I had some questions on magnifier systems posed in the letter HDN
> Original Poster: Christopher Renning <crenning-at-rz-online.de> 
>   Date: 28 Dec 93  12:51:00
>   From: Richard Quick
>     To: All
>   Subj: 10KVA Tesla Coil
> Well I hope everyone had a happy holiday. I am now recovered
> enough to post some more specific info on Magnifier construction
> and operation. I have covered some general material on this
> revolutionary Tesla coil system, but will now endeavor to throw
> out some specific pointers for those of you who have an interest
> in this much more efficient RF power processor.
> As I have mentioned the Magnifier is a three coil system. The
> primary is excited from a Tesla tank circuit, the secondary coil
> is inductively coupled to the primary, and the extra coil is top
> loaded on the secondary in such a fashion as to be uncoupled
> completely from the primary/secondary "driver" coils.
Isnt the magnifier info quite different from that used by tesla in Colorado
Spring Notes? Can anyone on Tesla List direct me to a Richmond, Va coil
group whose founder published a commentary on the CSN? (The name escapes me)
It was my understanding that the extra coil tesla used as a tetertiary
existed INSIDE the area of the large 100 so ft primary/secondary exciter
circuit and therefore is coupled (perhaps loosely) inductively with the
secondary. Also on 7/19/99 in CSN he notes that the extra coil should be 3/4
wavelength for obvious reasons. Since the outside coil secondary is normally
resonated by the primary at 1/4 of the secondary wavelenghth the extra coil
should then be a third harmonic of the outside freq according to this
thinking? Isnt it possible that the extra coil could have been entirely
unconnected by wire to the secondary, (in what is reffered to as top loading
or base line connections) and that the high voltage effects displayed by the
extra coil produced solely by induction effects as demonstrated by the
primary and secondary of an ordinary TC where the parts do not have a common
line connection?
 The extra
> coil is base fed by transmission line, which can be anything from
> Litz wire, copper pipe, or heavy DC transmission wire.
This then implies that the secondary grounding has the same ground as the
extra coil?
> The keys to getting an efficient Magnifier setup in operation can
> be listed fairly easily: Close coupling between primary and
> secondary, good gap quenching, and proper impedances in the
> secondary driver and the extra coil.
> Coupling in Tesla magnifiers must be tight. Classic style
> vertical helix primaries are very practical for use in Magnifier
> systems, but heavy insulation between the coils must be used to
> prevent flash-over. The close coupling reduces somewhat the VSWR
Can one define VSWR acronym?
> in the driver secondary, and the 1/8th wave output contains
> substantially less voltage than a normal 1/4 wave Tesla system,
> but the close physical proximity between coils means flash-over
> will be a problem. Use several layers of polyethylene plastic
> around the secondary, and insulate the top primary turns with
> heavy vinyl hose. It has come to my attention that tapping the
> primary coil from the bottom turns, and heavily insulating the
> top turns, reduces flash-over. (now gee, why didn't I think of
> that?)
> Good gap quenching is a must. Because the coupling is so much
> tighter in Magnifier systems, more strain is put on the main
> system spark gap. If ever there was a need for exotic spark gap
> systems this is it. Quench times must be low, low, low, in order
> to trap the maximum energy into the secondary driver. An un-
> quenched (closed) gap will allow energy in the secondary back
> into the primary/tank circuit. This must be prevented. In
> Colorado Springs, Tesla used a pair of air blast gaps in series
> with a massive rotary. He kept pushing his line frequency higher
> (he had a massive, variable speed alternator in the lab),
> increased his break rate (up to 50,000 bps) and kept the energy
> delivered per pulse down to a minimum. The reason he strove to
> keep the energy per break down was to prevent overloading his
> gaps. As energy per break (voltage * current) increases, quench
> times decrease and efficiency in the Magnifier drop off. The
> increase in the number of breaks per second allowed the total
> energy processed to climb to unheard of levels, with unheard of
> performance and efficiency.
> The next key point to building and operating a small to medium
> Tesla Magnifier is proper coil impedances in the secondary driver
> and extra coil. The extra coil must have a higher impedance than
> the secondary driver. The extra coil must be lower in resonate
> frequency.
If it were 3/4 wavelength it is easy to see that the impedance would be
higher because three times as much wire is being used with loops being much
smaller dictating many more turns proportionally to the former secondary
case.However it just occured to me that such a coil shouldnt vibrate as a
3rd harmonic or 3 times the frequency, but should vibrate at 1/3 the
Can harmonics go in both directions to produce both lower AND higher
> I have mentioned here that the 1/8th harmonic output of the
> secondary driver coil matching the natural 1/4 wave resonate
> frequency of the extra coil is the most efficient mode of
> Magnifier operation. This is true, but don't get bogged down with
> it. This system will work and fire (within reasonable limits)
> with any extra coil that has a higher impedance and inductance
> that the driver secondary. Let me give some tips.
Does this imply that the extra coil has half the frequency of the driver
> I have found that most high performance 1/4 wave secondary coils
> make lousy driver secondary coils in the Tesla Magnifier. The
> reason is the impedance and inductance are too high, and the 1/4
> wave coil is not designed or constructed to handle high current
> outputs. 1/4 wave coils built per my instructions (posted here
> several times) are designed to produce excellent 1/4 wave voltage
> peaks, not 1/8th wave current. Your best bet is to wind a special
> coil for use as a driver. With this in mind what type of coil
> design would work best? Well my first decent driver coil was
> built for use as a 1/4 wave resonator, but it dropped into the
> role of a Magnifier driver without complaint; it had a nice low
> aspect ratio, and it was wound with heavy stranded wire...
Is low aspect height/width?
> A good general purpose Magnifier secondary has a very low aspect
> ratio for good tight coupling over the entire winding length (say
> about 1.5:1). It is wound with heavy stranded insulated wire (say
> #18 or larger) to help carry heavy RF currents with lower losses.
> The frequency of the coil should not be too low, say in the area
> of 400 kHz for most medium systems.
> For the extra coil you want to pack a lot of inductance into a
> small unit volume, but not too much. You will end up with an
> amazingly short resonating coil if this is done properly. Use a
> 6" or 8" coil form with an aspect ratio a little over 2:1. For
> winding the coil use say #20 -#24 double Formvar magnet wire. The
> extra coil must be heavily top loaded with toroid discharger in
> order to produce really killer performance, as is the case when
> pumping a lot of energy through any magnet wire coil. The
> impedance in the bare extra coil must be higher than the driver
> coil by some margin, and the frequency of the extra coil should
> be brought down around 200 kHz by top loading the coil with
> discharger. The impedance of the driver must be low (heavy
> stranded wire spaced by insulation) while the impedance of the
> extra coil must be high (thin magnet wire, close wound turns)
> The tank circuit of the Magnifier must be tuned to the same
> frequency as the extra coil with discharger. Set the driver
> secondary inside the primary and run a transmission line some 6-
> 8' to the extra coil. The extra coil must be away from any
> field damping effects such as ground, large metal objects, other
> coils etc. It must be allowed to resonate as freely as possible.
> Tesla List wrote:
> > Original Poster: "Brian H Le Page" <brian-at-oneau-dot-com>
> >
> > I am looking for information to start me on the way to designing a
> > magnifier.  Can anyone point me at relevant web sites etc that would get
> > started.  When I know a bit more I may then be able to ask some
> > questions.
> >
> > Thanks.
> >
> > Dr B.
> > Brian H Le Page, Ph.D, Fleet, England
> > 'Scientific progress goes boink', Bill Watterson, 1991

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