Re: Signal Generator or whatever

From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Monday, December 08, 1997 3:14 PM
To: 	Tesla List
Subject: 	Re: Signal Generator or whatever

A real simple answer:

> From:   Alfred C. Erpel[SMTP:aerpel-at-op-dot-net]
> Sent:   Sunday, December 07, 1997 6:55 PM
> To:     Tesla List
> Subject:    Signal Generator or whatever
> Hello All,
>     I would appreciate anyones opinions/ideas on the most accurate method to
> identify the natural frequency of a coil. I intend to purchase a function
> generator of some sort and use it determine the point of highest Q.  Is this
> the best way? If so, what is the cheapest/best function generator?
> Regards,
> Alfred

One with an output impedance = 0 Ohms. That removes the generator 
from the equation. The next thing to avoid false answers is to ensure
that the coil is isolated from its surroundings by the highest degree 
possible. That includes a sniffer probe from the scope. I have 
measured Q's (corrected for the 7 Ohm generator impedance) approaching 
500 with a scope probe suspended over 6' away from the coil. In real 
operational life one doesn't worry too much about isolation to this 
degree but if you are comparing coils and want to eliminate all 
outside influences, this approach is a *must*. My best resonator 
clocks in around 300+ on a dry day with a modest topload.