TC Tuner... wasRe: Dual layer primaries

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

One mod I would make to Terry's design is to wire the pot so that you turn
it counter clockwise to increase the frequency (i.e. reduce the resistance),
and then put the dial on the pot shaft, with a fixed pointer on the case.
The audio taper is pretty close to a 1/x, so the frequency scale winds up
being pretty linear on the dial.  Now you know why the old HP oscillators
have the dial on the knob....

You can also calibrate it against an AM car radio... It puts out nice strong
harmonics at odd multiples of the set frequency, and most AM radios in cars
these days have a PLL synthesizer, and are calibrated to within a kHz.  If
you set the TC tuner to 100 kHz, connect a wire wrapped around your car
radio antenna, you should hear a nice strong signal at 700kHz, 900 kHz,
1100kHz, 1300 kHz and so on.

If you want the ultimate in accuracy, you can try to zero beat it against an
AM radio station, since they control their transmit frequency to within a
few Hertz (particularly if they are broadcasting in AM stereo).  Say I
wanted to cal against Radio Disney here in Los Angeles at 710 kHz..  Tune in
Radio Disney.. Now, fire up the TC Tuner with the wire attached.  Set it to
about 100 kHz and slowly bring up the frequency until you hear the "squeal"
of heterodyne of the 7th harmonic against the radio station.  Keep
increasing until the squeal drops in frequency until it turns into a sort of
throbbing, and then finally until it just sort of fades in and out.  Now,
the TCTuner is set to exactly 710/7 kHz... mark the dial.. Repeat for other
stations and other harmonics...


>
> Terry's TCTuner is something to consider. I've used it with great success
> in conjunction with a frequency
> meter. Also, contrary to someones statement a few emails ago that the
tuner
> is already calibrated is not
> correct. The tuner should be calibrated if one uses the dial position as a
> representation of the
> frequency, however, I don't use it this way because a small change in the
> dial can be a large change in
> Fr. I simply find Fr with the dial, then, take the tuner away and measure
> the tuenr itself with a
> frequency meter (because I have one handy and it's far more precise). The
> tuner is very easy to build and
> comes in real handy for a great deal of misc. experiments like this.
>