Re: Tesla Coil Blunderbusses

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Duncan,
          Best I can do is from memory short of repeating the expt to 
get actual msmts. k was around 0.15 so the LSB would have been around 
Fr/1.07 (about 93 - 94% of Fr) - about 7% off tune roughly. Obviously 
the exact figure depends on ksys which is why the diversity of 
figures I expect.

Regards,
Malcolm

> This was apparently a well-known phenomenon in the days of spark
> wireless, but has for obvious reasons been forgotten over the decades.
> I only came across it when thumbing through an old book on the topic.
> An illustration from this book ("Handbook of Technical Instruction for
> Wireless Telegraphists" by H.M. Dowsett and L.E.Q. Walker, 8th edn,
> Iliffe, 2nd impression 1947) showing how the peak secondary current
> increases dramatically when the primary and secondary are slightly
> detuned, I have scanned and stuck on my webpage at:
> 
> http://home.freeuk-dot-net/dunckx/wireless/inductive/inductive.html
> 
> The relevant bit is around 3/4 of the way down the page, just after
> the illustration showing the effect of varying the coupling.  Note
> that Dowsett & Walker obtained these curves from an experimental test
> circuit (sadly unspecified) designed to show the effect clearly and
> that this circuit had an optimum detuning of around 11%.  They say
> that the average spark transmitter/aerial combination should be
> detuned around 3%.  It'd be interesting to know how this compares with
> Malcolm's experimental observation on a TC.
> 
> Dunckx