Splitting & Tank circuit

 * Original msg to: 102505.61-at-compuserve-dot-com
 * Carbons sent to: usa-tesla-at-usa-dot-net

Quoting Scott Myers <102505.61-at-compuserve-dot-com>:

> About the situation called "splitting", where arc dance up and
> down the secondary. Why is it called this?

Because the secondary coil is overdriven, and cannot cleanly
handle all of the input energy on just one standing wave. The
coil frequency actually splits with the excess energy
establishing parasitic standing waves in the winding. These
parasitic standing waves are higher in frequency than the natural
1/4 wave frequency of the winding. Because these parasitic
frequencies are higher, their 1/4 wave voltage peaks occur at
points below the top of the coil. The sparks that jump up and
down on the outside of an overcoupled coil are the visible 1/4
wave voltage peaks of the higher "split" frequencies.

> On tank circuit designs;  I have seen two types mainly used, 
> one with both legs of the pole transformer connected to the 
> tank circuit and the other grounding one leg of the transformer
> and primary.  As I have been told, you use both legs in your 
> circuit.  D. C. Cox of Resonance Research grounds one side of 
> his circuit.  In the output I have seen, there seems to be no 
> difference. Recalling my electrical theory, there should be no
> diference in either one. Both provide the same HV potential.

> You have been doing this awhile.  Have you tried both methods? 
> What has been your experience. It seems that the grounded 
> method should be safer as it give the primary cap a bleed path
> after the transformer is powered down.  Comments? 

I have done a fair amount of experimentation with many different
tank circuit configurations. So has Tesla, and the COLORADO
SPRINGS NOTES contain a wealth of information on performance
characteristics of various tank circuits. In general I prefer
tank circuits where the primary is ungrounded or "floating". 
When using these tank circuits I always use a safety gap with a
grounded center post to provide a ground reference when required.

Tank circuits that oscillate or "ring" off of the RF ground
require rather extensive RF grounding systems to achieve the same
high Q factors as a tank circuit that is floating. The drop in Q
factor is easily seen on an O'scope when one side of the tank
circuit is moved to ground. I have noticed that the tune on tank
circuits that ring off the ground tends to be "mushy" or lacking
in sharp frequency response. Any time you ground one side of the
tank circuit, the length of conductor in the ground path must be
considered as a source of parasitic "off-axis" inductance (not to
mention unwanted resistance). The difference in tuning sharpness
and measured Q is usually so pronounced that I always recommend
obtaining two bushing transformers and using both bushings for HV
feed to the coil rather than forcing one bushing to ground

The exception would be a transformer with only one high voltage
bushing, were the secondary winding of the step-up xfmr is
grounded inside of the case. This is a common configuration on
many surplus pole pigs. What I recommend doing then is obtaining
a matched pair of these xfmrs and wiring the low voltage
primaries in parallel, with the HV secondaries placed in series
by common grounding of the cans. What you end up with is a pole
pig version of a neon configuration; you get two high voltage
bushings of opposite polarity with a case grounded center tap.
The other option on pole pigs (assuming sufficient voltage) is to
pop the lid and free up one side of the HV winding from the case.
Using some poly-insulated coax core for a high tension lead you
can drill a hole in the lid, pop in a nylon grommet, and buss the
high tension out to an externally mounted bushing. You will find
single bushing pigs already have the threaded hardware mounts on
the outside of the can for these optional, bolt on, insulators.

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12