Re: The PING Test

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
 
> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
> 
> Antonio -
> 
> It may be possible to make a Ping oscillator using a 555 but I have not
> tried this circuit. It may be necessary to add an operational amplifier to
> provide a low impedance source.

When the 555 oscillator output goes down, the impedance is low enough
for
a "ping" test. When it goes up, it is not. A fast op amp can provide
lower impedance, but it's a bit more complicated to power and bias
everything correctly.
 
> In Terman's Radio Engineer's Handbook he points out that the secondary
> voltage in the coupled circuit (Tesla coil) and the effective Q would be
> slightly lower than the actual voltage and Q of the secondary coil alone. I
> take this to mean that losses determine the amount of secondary voltage in
> the TC system. 

All talk about Q affecting the -maximum- gain of a TC-like system is
for continuous-wave, sinusoidal steady-state, conditions. Not for
operation by capacitor discharge.

> Do you have any comments on my question in the original post? Should the
> turns be increased or decreased to increase the secondary voltage and spark
> length with the same H/D coilform?

Increased. If nothing else changes in the coils, and the primary
capacitor is changed to keep the system tuned, the voltage gain is
increased. The input power may be increased too, since the primary
capacitor will be greater. Of course, excessive increase in the
losses (too thin wire), or the power supply not being able to charge
the modified primary capacitor, will reduce the performance. 
There is a maximum that can be reached before these problems start 
to be significant.

Antonio Carlos M. de Queiroz