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.