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Re: Q?

I would like to comment on one thing in this piece:

> Original Poster: Parpp807-at-aol-dot-com 
> 
> In a message dated 3/8/00 10:48:41 AM Central Standard Time,
tesla-at-pupman-dot-com 
> writes:
> 
> << Original Poster: "Raycroft" <k.raycroft-at-worldnet.att-dot-net> 
>  
>  >>>Hi all
>  
>  I've heard a lot about "q", but don't really know what it is.  Would
>  someone be kind enough to explain:
>  1.  How to calculate
>  2.  What it measures
>  3.  What it is useful for
>  Thank you very much for your time,
>  Jason Raycroft<<<
>  
>  Hi Jason,
> Q is known as the Figure of Merit for an inductance coil. Q = X sub L over R 
> where
> X sub L is the inductive reactance measured in Ohms. X sub L = 6.28 x fL 
> where f is the frequency in Hz and L is the inductance in Henries. R is the 
> DC resistance
> also measured in Ohms. Therefore, Q is a dimensionless ratio. The efficiency 
> of
> a coil increases with Q because with a low DC resistance the coil is able to 
> return 
> increasing amounts of energy to the circuit with the least amount of energy 
> lost to the DC resistance in the form of heat. A perfect coil has zero R and 
> infinite Q. As an inductance is tuned thru resonance, a high Q coil will
have 
> a very sharp response
> curve at the resonant frequency while a low Q coil will tune broadly. 
> Generally speaking, a high Q is desirable for a continuous wave coil. But in 
> the perverse nature of Tesla coils, a high Q is not always desirable for a 
> disruptive (spark gap) coil.

Why not?  I would go for minimum losses (read high Q) in anything 
bearing in mind that there are always tradeoffs to be made. For 
example, one might cram some more inductance into a secondary 
using smaller wire so that more inductance was required for the 
primary in turn raising the Q of the primary which is certainly 
desirable. In this instance, you are trading secondary Q for primary 
Q. The better option is to build a bigger secondary so maintaining 
secondary Q as well. 

Regards,
Malcolm
 
> I would urge you to reference any of the classic radio engineering texts
such 
> as Terman or Henney. There is also Circular 74 and the ARRL Handbook. John 
> Couture's Tesla Coil Design Manual is very good on how Q relates more 
> specifically to TC design.  
> 
> I hope this helps and my explanation rates a reasonably good Figure of
Merit. 
>  :-))
> 
> Happy day,
> Ralph Zekelman
> 
>