# RE: High Voltage Output

```Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>

In a Tesla coil, the pri-sec turns ratio is only indirectly related to
the step-up ratio.  The THEORETICAL ratio is governed by the ratio of
sec to pri inductance.  Notice the all-caps qualifier though.  The
theoretical voltage gain would only be realized if no losses occurred in
the spark gap, conductor resistance, skin effect losses, and if sparks
and corona did not occur.  None of this applies to actual coils however.

The firing rate of the gap and cap size affect only the power, not the
voltage produced.  Some losses may be somewhat lower when the frequency
is lower, so frequency may marginally affect the voltage.

The actual voltage produced by an operating coil is something that I'm
not sure has ever been accurately measured by anyone on this List.  It's
easy to estimate the theoretical maximum and apply some derating factor
that's been pulled out of a hat to account for losses, but it's just
slightly better than a WAG.

The actual voltage is something of academic interest, but little
practical use beyond bragging rights.  Ebay sellers generally claim nice
round numbers like 500kV, no doubt just pulled from the air.  Relative
performance of coils is generally quantified by citing straight line
point-to-point streamer length, and this correlates with input power,
not output voltage.

Regards, Gary Lau
MA, USA

Original poster: "Chris Fanjoy" <zappyman-at-hotmail-dot-com>

As someone relatively new to this hobby (still building my first TC)
I
haven't fully grasped all the principles involved. One thing that has me

puzzled is this: what determines the high voltage output of a Tesla
coil?
If not the step-up ratio of the coil itself, then how about:
-Firing rate of spark gap
-Size of tank capacitor
-Operating frequency of coil
-All of the above?
Just curious, as this may be something to consider as I design my own
TC.

Chris

```