TSSP: List Archives

From: "Malcolm Watts"
Date: Tue, 10 Sep 2002 08:40:18 +1200
Subject: Re: [TSSP] Quiz, Sec diameter question

Hi Greg,

On 7 Sep 2002, at 17:51, Greg Leyh wrote:

> At 01:16 AM 9/6/2002, Paul wrote:
> >[snip]
> >By way of encouraging coilers to delve more into the theory of the
> >subject, I thought of running a quiz game.  Something along the lines
> >of
> >
> >  http://www.abelian.demon.co.uk/tesla-quiz/
> >
> >Several of the questions would require a bit of thought and some
> >delving into web pages and text books.  Wonder whether something like
> >this would appeal to coilers, either as a one-off or an on-going game?
> 
> Perhaps if they could convert their Groat winnings
> into a plethora of TC parts, at the prize booth?  ^_^
> 
> 
> I've been mulling over the common wisdom of keeping
> secondary aspect ratios fatter than about 5 to 1.
> 
> What effect is it, that limits the performance of a
> secondary as it gets thinner?  It's certainly not
> Q degradation due to copper losses.

I wound a coil with an outrageous h/d ratio a couple of years ago to 
see what effects might be present. I never got around to properly 
characterising it due to a lack of an electrically quiet enough space 
but a quick look showed its Q to be pretty low and the response 
rather broadband with a lot of resonant modes present. I agree it 
can't be due to copper losses and the only thing I could think of was 
a rather poor L/C ratio. In effect, it was degenerating into a 
longwire. The diameter from memory was around 2" or less and length 
must have been around a metre or so. I think the wire was around 
0.8mm.

>  From a design standpoint it appears that a thinner,
> more densely turn-packed secondary offers both a
> higher resonant freq (Fo) and output impedance (Zo),
> without reducing the Q to unusable levels.

I never fired it but it would be interesting to see how it would 
perform as both 1/4 wave and 1/2 wave. It might also be fun to run it 
with a primary much too high in frequency. I would expect looping 
arcs of corona to form along portions of it as seen on another 
outrageous coil I once built.

Re the quiz, I've already started :)

Regards,
Malcolm


Maintainer Paul Nicholson, paul@abelian.demon.co.uk.