Re: spark gap and SSTC coil questions

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Mddeming@xxxxxxx 

In a message dated 3/29/07 5:44:48 P.M. Eastern Standard Time, 
tesla@xxxxxxxxxx writes:
Original poster: ben eells <squeels2171@xxxxxxxxx>

Hi guys, it's been quite a while since i've posted. I built 2 spark
gap coils with the help of the people on the list last year. I'm
thinking about building another coil but rather than just building a
bigger version of what i've already done i'd like to try something
different. I'm considering the SSTC. This is gonna be somwhat of a
challenge for me. While i have become relatively familiar with the
operation of spark gap coils (still no expert) i don't really
understand the operation of SSTC's. I know that i'm gonna need a
heavy duty transistor.

Much more than that An IGBT (a.k.a. "Brick")
It's been my observation that in spark gap
coils the streamer length is mostly dictated by your transformer
(obviously this is a simplified statement since variations in the
capacitor, spark gap, secondary winding etc will also effect the
overall performance of the coil. When all of these factors are
optimized it's the transformer that determines how much power your
other components have to work with. Also, it's generally the most
expensive of the components which means your streamer length is gonna
be determined by how much you want to spend on a transformer.) It
seems that the streamer length of a SSTC is dictated by the size of
the transistor much in the same way that a spark gap coil is dictated
by the transformer (in terms of difficulty of finding the correct
transisor as well as cost of the transistor).


YE$$$
Is this a correct
observation or am I way off on this assumption? I think the answer to
this question is yes which leads me to my next questions.

My next question is would it be possible to build my own transistor?
coilers have been building there own caps for years so this doesn't
seem to far fetched but i haven't found much useful info on this
subject. If anybody knows of a way to do this I'd like to hear about it.


Unless you have all necessary tools that operate on the microscopic level and
a way to produce chemically pure silicon, you can't make a transistor or SCR,
or IGBT,

An alternative to my first question is would it be possible to build
a multiple mini transistor? I think the answer to this question is no
but I'll admit that i know little about transistors and as far as
electrical components go these seem be fairly hard to actually
understand. (I can already see the jokes about using a pentium 4 to
operate my coil pouring in.)

They'd have to be so perfectly balanced in their response that even
NASA specs wouldn't be sufficient. (i.e. you couldn't afford them.)


Now for something completely different. A long time ago I posted a
link to a site showing how to modify a NST from 7.5k-
7.5k+   to   15k-. The site is here.

<http://www.rtftechnologies.org/emtech/nst.htm>http://www.rtftechnologies.org/emtech/nst.htm

I asked if this modification had any relevance to coiling and the
answer i got (along with other answers) was no because there is no
increase in the transformer performance only the orientation of the
voltage in relation to ground was changed. After thinking about this
for a while I've come up with more questions. From what I understand
by performing this modification I end up with a sine wave with a peak
to peak voltage of 15k (is this correct?) and since it's 0-15k it's
direct current (is this correct also?)

Using the circuit as shown  will produce a pulsating DC output to charge
your cap that looks like this:
________________
UUUUUUUUUUUU

 Where the peaks occur 120 times a second, NOT a sine wave.
If i'm right about this it
stands to reason that i could set my SRSG for 60 breaks a second
double the capacity of my MMC and make some really big sparks. Since
it's DC i wouldn't have to worry about the capacitors discharging
back into the transformer and could theoretically have even fewer BPS
and have even longer sparks. would this be possible? If i'm correct
and the transformer output is DC i'm worried that it's gonna totally
screw up the way the coil works and have an end result of alot of
power going through a coil that doesn't produce any streamers. Even
if this doesn't work the way I'm predicting i'm bound to get some
valuable feedback and as always it will be greatly appreciated. Thanks





You won't have to worry about NST resonance, but you will still need

SQRT(L x C) pri = SQRT(L x C) sec for resonance. if you double the 
cap size, you must either reduce to primary inductance by 50%, or 
increase the size of your secondary or topload to give you 1/2 the frequency.

Since in a standard TC, your already floating the NST secondary 
terminals, I don't see any real gain here.


Hope this helps,

Matt D.







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