Re: why TC Different from others?

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

Original poster: "Jan Wagner by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>

Hi,

On Fri, 20 Dec 2002, Tesla list wrote:
 > Original poster: "J Dow by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
<jdowphotography-at-hotmail-dot-com>
 > I am an average guy that got into coiling. I'm fairly intelligent and a
 > quick learner so coiling wasn't all that hard to pick up once I started. I
 > was never educated in electronics. So please forgive this question.
 >
 > A TC primary and secondary form a transformer. The TC transformer produces
 > RF when it operates. 1. Why don't other transformers with similar winding
 > ratios produce RF?

It isn't really the winding ratio that produces the RF. It's the
oscillating tank.

 > The TC transformer is part of a "Tank" circuit. The Capacitor the primary
 > and secondary "Ring" or oscillate when the capacitor discharges. As I
 > understand it, the Pri, Sec and Cap oscillate at (RF) very high frequency.
 > 2. Why doesn't a NST or other transformer Ring at RF when it is part of a
 > tank circuit?

The NST isn't part of the oscillating circuit (tank), it's just there in
order to charge up the tank with some energy. When the spark gap breaks
down, that energy is passed as RF to the secondary and the streamers.

When the spark gap breaks down, it will at the same time short out the
NST, so the NST isn't part of the RF circuit.


 > Or perhaps it does.
 > 3. Why do we get 60hz when it rings at
 > higher frequency?

It's not necessarily 60Hz. But low frequency anyway.

While the tank rings at RF, it is still charged up from a low frequency
supply.

One mains cycle (60Hz or other) has a positive and negative peak, i.e. two
peaks per cycle.

This means the tank cap reaches maximum voltage (positive, negative)
twice in a 60Hz cycle.

Now if the the spark gap correctly breaks down each time at these peaks,
then the RF tank will oscillate up and decay two times during one 60Hz
cycle, right?
This means that the streamers end up being pulsed at 120 Hz, and voilá,
here you got your low frequency content in the streamers.

IIRC there are some pics and oscilloscope waveforms at
   http://www.richieburnett.co.uk/tesla.shtml
(and Richie also explains TC operation thoroughly at
  http://www.richieburnett.co.uk/operation.html  )

About mains being 50Hz, 60Hz, etc: this has historical reasons. Of
course, there's also a limit to the frequency, as you don't want the
mains cabling to radiate/transmit all over the place.

cheers,
  - Jan

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  Jan OH2GHR