Re: What's around the toroid is important....

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Jeremy,

At 10:26 PM 5/7/2003 -0700, you wrote:
>Hi all,
>......
>
>Calculated Resonant Frequency: 215.24kHz
>Measured Resonant Frequency: 214.3kHz
>(The meter has a +- tolerance (1 or 2%) ... )

It has gotten to the point that the programs and calculations are more 
accurate than most meters :-))


>Interesting things to note:
>
>I've used Terry's TCT to find the resonant frequency.
>I modified the design slightly to allow more precise
>control of the frequency knob. It goes from 100 to
>300kHz with most of the pot's movement being from 100
>to 200. (Where my current coils live ... :) )

Cool!  I gave the original a very wide range to cover "everyone's" 
TCs.  But it is easy to tighten in the band to give much more precise 
adjustment for one's own range of TC frequencies.


>The meter's - lead is connected to the ground clip
>and the + lead is connected to the base of the coil.
>
>When I back off to about two feet or more away from
>the  toroid, the meter instantly switches to the
>harmonic of 430kHz. If I wave my hand within two
>feet of the toroid, the meter finds the resonant
>frequency once more. Also, get this: when I yank
>the + lead out of the meter and leave the ground
>lead in, it reads the resonant frequency no matter
>what I do. :) (Who said this was a science? Explain
>that one, someone....)

So many stray effects mixed with the meter's digital electronics...  Hard 
to say what exactly is going one there.  Seems like something is doubling 
the frequency.  Maybe a reflection from the square wave edges of the 
TCT.  No worries as long as you can get it to lock onto the real 
reading.  Real frequency counters have attenuation, AC/DC coupling and 
level controls to weed out the stray signals.  Little meters just "try" 
;-)  When you move around the coil something is just re tuning things a 
little which pushes something else over the edge.  Not a big deal.

Cheers,

         Terry