Re: 3 probably awful beginners questions ;-)

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

Original poster: "Barton B. Anderson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Christoph,
Congrats with the first light!
Comments interspersed:

Tesla list wrote:

>Original poster: "Christoph Bohr by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <cb-at-luebke-lands.de>
>
>1: I Use a 10KV / 40Ma Power-Supply with a 11nF cap at about 185KHz. The 
>Tesla-Calculator I have tells me I won't ger more power / longer arcs by 
>increasing the xformer's powerlevel, is that right?

Is this your personal file or a program off the internet? Which one is it? 
The calculator and your coil should both show an increase in spark length 
with an increase in power. How noticeable depends on the amount of change 
and performance of the coil.

Also, 185kHz appears low. I would expect 250kHz to 290kHz range even with 
your coil loaded with the toroid. Is this a measured frequency (signal to 
the base of the secondary and o-scope probe dangling at toroid height about 
2 coil lengths away (or similar)?

>I only get 14" arcs to a grounded point with a 900 turns coil ( 1,5ft 
>high, 4"dia  with a 4"/15" toroid ) and I wonder if more Power would get 
>the thing done or if the cap  justcan't store more energy.

The coil could realistically near 30" spark lengths at 400 VA, thus 
indicating considerable losses are in the system.

>2.: I measured out the coil with a signal-generator ( hope the term is 
>right ) and oscilloscope, but with the values I received the coil wouldn't 
>work at all, so I tuned by hand an It started working.( far away from the 
>point I measured out ) But I can change almost 1 turn up/down on the 
>primary with no measurable difference in performance, is that normal?, 
>shouldn't there be en exact point?

Sure there's an exact point. But often, a coil with a relatively wide 
bandwidth in conjunction with low % of Fres due to primary LC values used 
causes this. In other words, the change in L per turn may result in a 
slight change in frequency in comparison to the bandwidth. This slight 
change results in the ability to move 1 or more turns from Fres without 
much change in performance. Actually nice if when further considered. My 
8.5" coil can move a couple turns out or in. If I move too far in, I begin 
to get erratic sparking and racing sparks which I attribute to tuning at 
the edge and then spark loading takes it further beyond it's capability. 
Thus, tuning outward slightly prevents spark loading dilemma's. This isn't 
to be confused with coupling. That too can cause racing sparks if too high. 
My bottom line is this is perfectly normal and due the coil values.

One example of the LC values of your coil. A 1 turn change outward results 
in 7.8% Fres change. Assuming the bandwidth is wide enough to tolerate a 
greater percentage off of Fres, then this shouldn't be a problem. But 
assume you tune for a  0.1uF cap. Then a 1 turn change from it's (then) 
tuned point would result in a near 20% change from Fres. The coil may or 
may not tolerate it. In the other direction, tuning for a .001uF cap size, 
then a 1 turn change results in a near 3% change in Fres. Of course, this 
is just for your coil. Other coil parameters present various combinations 
of this.

>3: My sparc-gap ist a static with an fan, rather unprofessional design. 
>When then Fan is at full power ( this takes aprox 3 secs after Power on ) 
>the arcs get a little longer but I get very very bright arcs from the 
>ground point of the SEC to the inner winding of the PRI, may my coil be 
>extremely out of tune but run anyway?

Hmmm. Not good. This will burn your secondary winding at this point. I do 
wonder if your tuned to the next lower resonance, but I haven't looked to 
see where that would fall nor have I tried tuning down and running at a 
lower resonance, so I don't know what might occur in that mode. But 
definitely a bad thing.

>the two parts are about 3 inches apart, so at about 15 kV I thought 
>nothing should go wrong.....?! may this be the point where I loose Power? 
>( I#m almost sure a arc of that size will consume a lot of power, ) I saw 
>qiute similar coils having almost 3 times the arc-legth..

If the distance between primary and secondary is 3", there should be no 
problem arcing due to arc voltage distance, but then I'm guessing at your 
primary style. Maybe some more info will help point to the problem. Maybe 
list the primary type style and position up and down in relation to the 
secondary.

Take care,
Bart