Re: Why the difference in Fo WinTesla & Fantc?

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

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

Hi Brad,

Tesla list wrote:

>Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><CoolCorals-at-aol-dot-com>
>Thanks for all of the info and pics!  I did find that I had inputted the 
>primary in a bit wrong under Radius.  I used the 2" Inside and for the 
>other radius 2" plus .08".  My primary looked bent, but seeing your pic 
>and layout, I understand I messed it up.  It does show a much more 
>accurate L as you showed.

Excellent. Glad to hear it's working out.

>On the Torroid, you show it down over the secondary quite a bit.  Will 
>this work better than bottom plate flush with the secondary, 2" up from 
>secondary or like you show it "sunk" into the secondary?

No. When I run specs, rarely were given data to identify coil(s) and 
toploads height positions from ground, etc.. I use 20" coil height out of 
habit (happy medium) and typically place the toroid center height at the 
top of the secondary (just a point of reference, and again, a habit). The 
toroid height affects frequency slightly. No big deal. Typically, the 
toroid height is positioned a couple inches up. Keep in mind when the 
toroid height is too high, breakout can occur from the top of the secondary 
coil instead of the toroid. Keep the toroid low enough to prevent this and 
reduce corona (if visible).

>My primary IS a helical coil.   Sorry I noticed that I hadn't written that 
>on the post.

Yes, that's what I thought. Thanks for clarifying.

>I have a question here, doesn't the Inductance of the whole primary plus 
>tank wires determine the total Tank Inductance?

Yes.

>I was hoping to then shorten the wires to adjust frequency.  If with no 
>wires im at .0059mH and with all wires .0095mH (as tested), this would 
>allow for a cap range from .0175uF - .0108uF while still maintaining the 
>500khz.  That goes from under my ballast max to well over, so can I just 
>tune my tank wiring for this?

Yes, you can simply move the tap. Your tested value (9.5uH) is equivalent 
to a 9.5 turn on your primary. Removing 2.5 turns will take you down to 
your current 7 turn primary. Thus, 7 - 2.5 = 4.5 turns as an approximate 
tap point in reality. This is what I meant when I said that due to the 
external wiring with your particular coil, the actual tune point may be 
less than 7 turns. Only actual testing and probing around when you tune it 
will tell the tale. The point here is that you will be able to tune the 
coil via the primary connection (tap).

>   Is the reason for keeping tank wires short so that most of the 
> inductance is in the actual primary?

The effect of your coils external wiring is significant. But in many coils, 
the effect is small. For example, my primary is 102uH vs your 5.4uH 
inductance. In many cases, it's not of great concern if kept within reason. 
All the miscellaneous variables could be hashed out, but that would be a 
whole different post.

>   Like in my case if the tank wires have essentially doubled my 
> inductance, then the energy stored would also be split 1/2 in tank wires 
> and 1/2 in Coil??

By the time your actually tuned in, yes. Ref post from Antonio.

> >Well, due to the tuning issues you will be running into, I wouldn't go up
> >in capacitance. Reducing capacitance will allow more turns.
>
>      Yes, I thought that reducing C would be best, and also make less 
> work for the ballast.  This is why i went to .0107 on the MMC, to better 
> match my tested inductance at 500Khz.  I have been told though that these 
> Caps will not work for this high of frequency.  My RLC tested them with a 
> Q= .1 or less.

I'm not sure on the cap type, but if someone mentioned this to you, they 
may be correct. You should verify with the many users on the list here.

>I do know that my H/D ended up rather high.  Most seem to like from 
>3:1-6:1 whereas I'm 10:1  what does this affect?

Hard for me to say. I haven't built an h/d that high. I know some have had 
poor performance with h/d's that high. Some have expressed good results 
with relatively high h/d's, but I don't recall those particular heights. I 
think you'll get output from the coil. What kind of performance or other 
phenomena I couldn't say.

>Where would you set the spark gap if I have 3 total Gaps and 6Kv?

Well, I think you said there are four 1/4" electrodes for a 3-series gap. 
So I would set the total gap distance at 0.16" (0.053" between each 
electrode). This yields an arc voltage at 8.2kV (I assumed 6Kv was rms 
which is 8.5 kVpeak). Should get you very in the ball park for 1/4" sized 
electrodes.

The gap spacing should remain adjustable.
A simple adjustment with 4 electrodes can have 2 electrodes on top and 2 on 
bottom (offset to centers):
------------------------------------------------------
o o    <= top set. Make adjustable toward bottom set.
o o  <= bottom set. Make stationary.
------------------------------------------------------

>Also, I do have tested Q ratings for both the primary and secondary.
>My RLC has that function.  The primary's Q= .25 and the secondary's Q= 
>3  What does this tell me other than the relationship of true reactance to 
>resistance?

Not much. Probe loading spoils the Q. What you'll want to do is actually 
measure with a scope antenna of some type. Good readings will be best with 
a lowZ amp on the front end of a generator. Pinging the coil is maybe the 
best approach I'm aware of, but not sure what type of equipment you have at 
your disposal. There are various methods and some approaches are better 
than others. Terry has papers at his website on various tests he's 
performed and he does a great job at documenting his method and tools of 
approach. Also look through his misc files. I believe there's a low Z amp 
circuit drawn up. Don't be frightened if Terry has the best equipment 
around. Many of us simply have generators, scopes, and the typical tools. 
His equipment has been used to derive some very accurate data for various 
tests. Paul's TSSP website also has various tests performed by the TSSP 
group. These are a couple good web sites to see how others are performing 
some of these measurements. I'm not sure if it's something you want to 
actually do now, but I'd recommend reading up on it. The List Archives and 
pupman-dot-com is also a good place to search past posts on Q. There's a whole 
lotta info in those archives.

http://hot-streamer-dot-com/
http://www.abelian.demon.co.uk/tssp/

Take care,
Bart