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Re: Characterizing my Secondary

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Mike,



At 11:03 AM 6/26/2005, you wrote: 
 Hi All,

I'm probably jumping ahead a little but I'm curious.

 My coil is wound on an 8-1/2' by 42' plastic tube.
I wound and varnished an 8-1/2" by 39-7/8" coil on the tube.
I figure about 1400 turns of #22 wire.
I hung the coil horizontally 3 ft off the floor.

You should put it in the same position you coil will be running. the surrounding floor and room will affect things greatly:

http://hot-streamer.com/andrewb/models/models.htm

I lightly coupled a signal generator to the coil.
( I had the Gen. wires a few inches from the coil)
I put the 10x osc. probe near the coil to pickup the signal.
I found a self resonance at 204,620 Hz.
The Q was about 225.

You can feed the base of the coil with a sine wave from the signal generator. A piece of wire hooked to a scope probe 5 feet away will easily pike up the resonance as the frequency is varied. Try not to hook anything to the top of the coil (top toroid is ok ;-)) The scope probe will load down the sensitive coil resonance too much and foul the reading. Only the Tek 5100 probe is able to do that and they are $$$$.


I then connected a 100 pf. polystyrene cap. across the coil and
found a resonance at 54,081Hz with a Q of 232.


you can find the Q from the (F2 - F1) / Fo method which I think you know.

 Using the formula;
L = 1 / (4pi^2 f^2 c)


Fo = 1 / (2 x pi x sqrt (L x C)) is the formula you want to use.

Don't use C or wire length stuff!! The wire length has long been shown not to matter...

Cheers,

        Terry


I get 87mh for the inductance of the coil.

Does all seem about right?

                  Mike

P.S. When I connected the 10x probe (15pf. 11meg.) across the
coil it resonated at 95,860 Hz. Q= 100