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(Fwd) Re: Extra coil



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

Robert,
        A "whoops" on my part.......

On 9 Feb 2002, at 10:17, "Tesla list" <tesla-at-pupman.co wrote:

> 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 ;).

I re-read your post and realize that the "extra" coil was inductively 
coupled to the other two, not a trap connected in series between 
them. Sorry. However, that still doesn't mirror Tesla's extra coil 
connection.
       I did a very similar thing on my first mains-powered coil. The 
primary Q was shocking (NPI) as it tuned with just a single turn (I 
was in the process of discovering how a TC worked). I wound an 11 
turn coil, tuned it to the secondary with a transmitting ceramic cap 
and positioned it directly above the primary turn. Output increased 
greatly. In that case, coupling between the primary and secondary was 
increased and since there was now circulating current in another 
circuit without a spark gap in it, primary Q was effectively boosted.
But it was not connected as a Teslarian extra coil.

Regards,
Malcolm
<snip>