At 08:12 PM 8/12/2004, Peter L. Peres wrote:

>You want the inductors coupled imho. the way they are set up now, you see
>four parallel RLC resonators in series towads a load, and they form an
>efficient bandpass.

I understand, but I'm trying to model an existing device that deliberately set them up with minimal coupling. Most designs would use a single large inductor, but LARGE is the word, at about 3.5" diameter, and maybe 14-20 inches long.


>To make the inductor work as you want it, you have to have a coil whose
>self capacitance is much lower than the load's. This is nearly impossible
>in your situation.

Yes. About 6-ish pF is practical

> What you could try is to use a tuned parallel circuit
>and couple the antenna at the top and the feed at a tap or small secondary
>to the coil. Or use an inductive antenna. Two crossed ferrite rods should
>work perfectly at that frequency.

http://www.dvanhorn.org/TankCkt.gif This is the circuit in question, which does work pretty well. I'm trying to optimize it.


>To continue the way you do it now, you would have to add a parallel
>resistor to each coil to reduce its self resonant Q below that of the
>calculated target Q of your desired assembly (with the rod). You are
>aiming for Q=2..10 probably, for each coil. Basically if the Q of your
>adapter is half that of the antenna + driver's then the antenna will
>dominate the tuning. The target Q must include the drive impedance.

Dosen't low Q make for instability?

>>The "antenna" isn't intended to behave as an antenna, in the classical
>>sense. It's a capacitor, starting with it's own value in the space, and
>>then increasing to some higher value as the hand is brought near.
>>
>>It's radiation efficiency is abysmally low.
>
>Ah, that's different. Still, for such a low capacitance at a low
>frequency, you should try to put the stick at the top of a parallel LC
>resonant circuit and either use it as a bandpass filter or as an absorber.
>The hand will detune it. The Theremin uses something like this (detuning
>parallel resonant circuit) for the volume control.

It does, but this is the pitch side.

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