Re: Extra coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Robert,

On 7 Feb 2002, at 12:06, Tesla list wrote:

> Original poster: "rheidlebaugh by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>
> 
> Just a thought as you 2 are discussing the extra coil. Before we had a tube
> radio we had crystal sets that, at best, tuned 2 stations at once with low
> volume. When we added an extra coil (3 coil system) the volume went up and
> we tuned only one station at a time. The extra coil increased the total Q
> and made the tuning narrow. Is it not likely that a similar effect is seen
> in the TC with the extra coil?  More power going into one frequency band and
> less power into the unwanted harmonic losses.
>    Robert  H 

Good question. First question from me: what was the exact arrangement 
of the crystal set before and after the extra coil was added? I 
suggest that in the first case, the load was coupled too tightly to 
the tuned circuit. In the second, the coupling was rendered looser by 
virtue of less total inductance under the influence of the coupling 
loop. Is there any reason that couldn't have been done with the 
single circuit? Presumably, the aerial was the same in both cases so 
no more power was available to the circuit.

    If you are close enough to the transmitter, you can have a 
reasonably good selectivity and run a loudspeaker from a crystal set using
a single tuned circuit (I live less than mile from several fairly powerful
radio masts).
     I have single 3" 1:1 resonator hooked to a few feet of wire in 
my study coupled to a bank of LEDs and self-tuned to one of these 
stations. One morning, a lightning strike put this station off air 
and despite the presence of another station right next door to the 
first and with 5x the output, the LEDs were off-air also. The second
station was still transmitting at full power as verified by another radio
set BTW.

     With reference to Tesla's circuit operation, things are totally 
different. It is being operated under transient drive conditions with 
a load that's anything but constant. In fact, Qsys varies from 
several hundred before output sparks start flying to somewhere around 
10 with attached sparks. This is easily seen by monitoring ringdown 
times on an oscilloscope.

      It is true that in the magnifier, Ksys is much less than the 0.6
coupling constant between the primary and secondary alone. In fact, it is
easily demonstrated experimentally that a similar Ksys appears in both.
There is also strong theoretical support for this and in fact, theory gave
rise to some key measurements which validated the theory. That implies
that energy transfer times (and hence primary losses) are the same for the
two systems if the primary systems have the same inductance and
capacitance.

      I've seen no evidence that a magnifier with an overall K 
identical to a 2-coil system can do better for a given power input under 
spark producing conditions. Under non-output-sparking conditions, both systems 
exhibit a broadened spectral response while the gap is conducting and in fact, 
if breakout is prevented, the magnifier can exhibit a greater one than the 2-
coil system after the gap has extinguished due to the presence of two coupled 
tuned circuits in the secondary/extra coil system.

Regards,
malcolm

> > From: "Tesla list" <tesla-at-pupman-dot-com>
> > Date: Wed, 06 Feb 2002 18:59:12 -0700
> > To: tesla-at-pupman-dot-com
> > Subject: Re: Extra coil
> > Resent-From: tesla-at-pupman-dot-com
> > Resent-Date: Wed, 6 Feb 2002 19:14:32 -0700
> > 
> > Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> > <m.j.watts-at-massey.ac.nz>
> > 
> > Hi Nele,
> > I must confess that I share John Feau's view of magnifier
> > operation. In fact, one of my first measurements on one confirmed
> > what he said and was previously postulated by Dr de Queiroz, notably
> > the value of Ksys. I too have read Tesla's notes on this but think
> > that what he thought and what actually happens are two different
> > things with respect to this particular form of TC. It is a nice idea
> > to think that the primary/secondary act like an oscillating voltage
> > source but in a disruptively-driven system they cannot for two
> > reasons: K for the pri-sec system is less than 1 and secondly, it is
> > driven from a charged capacitor (which runs down to empty), not a
> > voltage source (zero internal impedance generator).
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