Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
Hi Robert,
Thanks for the details........
On 8 Feb 2002, at 11:51, Tesla list wrote:
> Original poster: "rheidlebaugh by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>
>
> The original crystal set was made with a 100 T coil with a sliding tap for
> tuning. The coil was placed between earth ground and an antenna. A diode in
> series witk a high impedance earphone was shunt across the coil. The load
> reduced the Q of the coil and caused broad banding. A second version added a
> capacitor (variable ) in series with the coil and a seperate output winding
> of about 25 turns to the load. This improved the Q and tunability. A later
> version added an extra winding between the two. About 75 turns with a 600 pf
> capacitor across it forming a parallel tuned circuit between the input coil
> and the output coil.The volume encreased enough to drive a high impedance
> speaker( no longer made) with enough volume for a small room of people to
> hear.The extra tuned coil was connected to nothing,Just a hi-Q coil between
> input and output. No one moved the transmitter or the antenna to add volume.
V1 sounds as if you had a fixed capacitor for tuning and it was
tapped across varying portions of the coil. Correct? The change in
tap point alone would have caused the Q of the circuit to vary.
V2 sounds as if it had a degree of antenna matching introduced
by the variable cap between the antenna and coil. Also, a reduction
in circuit loading.
Without knowing the station/s frequency/s and inductance of the
75 turn coil it's difficult to know what action what is essentially a
bandstop filter between input tuned circuit and output coil was doing
but I bet that with 600pF across it, the Q wasn't all that high. But
that isn't quite the same thing as having an unshunted resonator in
series with the antenna and main tuned circuit. I'm having difficulty
relating that to Tesla's magnifying system (my problem, not yours ;).
The little setup in my study uses a single resonator with no
tuning cap between the aerial wire and ground. I designed it to be
self-resonant in conjunction with the antenna to a station
transmitting around 1.2MHz so the short antenna was used more
effectively (just a few feet of wire arranged as a short top-hat
vertical running up the wall and part-way across the ceiling). Even
with a load, the circuit is very selective. The higher power
transmitter I mentioned transmits on 567kHz.
I guess I will have to put another branch for experimentation
into the in-tray. I see at least a degree of antenna matching in your
setup.
Regards,
Malcolm
> Robert H
> > From: "Tesla list" <tesla-at-pupman-dot-com>
> > Date: Thu, 07 Feb 2002 18:32:44 -0700
> > To: tesla-at-pupman-dot-com
> > Subject: Re: Extra coil
> > Resent-From: tesla-at-pupman-dot-com
> > Resent-Date: Thu, 7 Feb 2002 18:53:54 -0700
> >
> > 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).
> > <snip>
> >
> >
> >
>
>
>
>