Re: 3/4 wavelength secondaries

To: tesla-at-pupman-dot-com
Subject: Re: 3/4 wavelength secondaries
From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
Date: Thu, 1 Aug 1996 13:33:07 +1200

Hi Ed Phillips, all,

> Question: Why the interest in free-space wirelength?
>     There have been a lot of listings here lately in
> which it appears that the author thinks there is something
> "magic" about having the coil operate near the free-space
> quarter-wave resonant frequency of the winding.  I can't see
> what difference this really makes, as long as the coil is
> excited at the correct resonant frequency as determined by
> self and lumped (top terminal) capacitance.  Am I missing
> something?
>     One other point.  Although I don't remember seeing
> it expressed explicitly, the effects of a top toroid are
> at least twofold:
> 1. The L/C ratio of the secondary is lowered, reducing its
> surge impedance and hence the loss of Q for a given power
> lost in discharge.  Seems to me this should increase the current
> when the discharge starts.
> 2. The breakdown voltage is increased, increasing the formation
> of the streamers which finally carry current when breakdown
> occurs.  In the case of one of my small coils, this effect takes
> seconds.

I think Skip said that he found he was getting longer and longer 
discharges the closer he got to matching the wirelength with
fr. Am I right Skip? There is another possibility too. Skip, are the 
best coils the biggest? If so, it may be that you are also getting 
benefits from maximising the radius of curvature of the system. I 
know Tesla mentioned this frequently and I think stated that he could 
build coils with no corona leakage if the r.o.c. was maximised.

Justapossibility,
Malcolm