[Prev][Next][Index][Thread]

Re: Optimal Quenching Tests

In a message dated 97-01-06 00:55:41 EST, you write:

<< snippity >>
>The really wierd thing, is that IF you quench at, or before, this point,
> the frequency splitting in BOTH the primary and secondary goes away. Ed
> Phillips and Richard Hull mentioned some time back that the grizzled
> veterans of spark radio knew all about this phenomenon, and used it in
> high power systems! The Corum's only rediscovered it - they probably
> hadn't yet been born when this approach was being used!   :^)
 
I wonder though, does the spectral splitting really go away, or are its
effects just minimized?  It seems to me that for the notch to form in the
first place, there must be spectral splitting occuring (this causes the
beating which causes the notch).  (more below).   Or do you mean that the
splitting goes away AFTER the quench?  There can be no splitting after the
quench since the primary is open, and can't interact with the sec, thus no
beating and no splitting occurs.   Splitting always stops at the time when
quench occurs, regardless of when the quench occurs, whether it's quench at 1
st notch, 2nd notch , 3rd notch , etc.

>  snip

>But, if you design a rotary gap that has much _less_ mechanical "dwell"
 >than the optimum (i.e., like John's "0 dwell" offset-electrode
> approach), and have a fast enough electrode seperation rate, mother
> nature will help you quench it at the right time.
 
 >> 5) My results seem to indicate that spark output falls off rapidly as
quench
 >> time moves outwards to the 2 nd or 3 rd beat freq. notch.  The 2 nd notch
 >> corresponds to  approximately the 17 th RF cycle of ringdown.  The 3 rd
beat
 >> freq. notch corresponds to approximately the 28 the RF cycle of ringdown,
in
 >> above TC example.  Most TCs  quench somewhere between the 3 rd, and the 6
th,
> > beat freq. notch--and that's with good quenching.  Who knows where poor
 >> quenching TCs quench?
 > 
 
 >It does! Most secondary energy that gets transferred back to the primary
 >is lost in maintaining the plasma in the gaps. Quenching performance
> also has a lot has to do with how much energy you're throwing off the
> top in streamers/ground arcs (the good kind of loss!). You can actually
 >have a fairly poorly quenching gap and still pound _lots_ of energy into
 >the secondary during that first energy transfer cycle. 

This makes a lot of sense; if most of the spark energy and length is already
given and produced before the first notch, then who cares what happens
afterwards, well you care, but it should have a minimal effect.  Of course
racing sparks may be a problem with poor quench, then again, following your
line of thinking, maybe there won't even be enough energy left to produce
racing sparks, if the Q is knocked down low enough?

>  Once you develop
 >heavy streamers, the secondary Q drops sharply, since it now appears to
> be very "lossy". Energy expended in streamers will not make it back to
 >the primary for the next trip around. This has the effect of reducing
 >the energy available to reignite the gap. Since gap reignition is
 >prevented earlier, this leads to an "effective" improvement in quenching
> performance. BTW, if you get an arc to ground during the first transfer,
 >_none_ of the secondary energy ever makes it back to the primary, and
 >you _will_ quench at the first notch. 

Very interesting,  This is something I never considered, (first notch quench
if arc to ground occurs). 
 
 >This may be why a seemingly poorly-quenching gap, such as Cox's
 >Milwaukee Museum coil with the beefed-up, but reliable, rotary
 >electrodes, can still belt out 10 footers! Even on my lousy
 >static/vacuum gap system, once the top-end really starts cookin',
 >"effective" quenching performance improves, and I'll hit 1-2 primary
 >notches consistently at 360-420 BPS.

This is really interesting, I wonder also if the use of tungsten electrodes
significantly helps the quenching on Cox's system, I remember that someone
suggested this recently on this list--that less metal is vaporized so it's
easier to quench.
 
 >> 6)  When I quenched at 8 us in the above example,  I saw no notches in
the
 >> secondary waveform;  I saw only a build-up, followed by a nice high
amplitude
 >> ring-down.  But yes, I agree, more work needs to be done to verify the
 >>  optimal quenching conditions needed for optimal spark output.
 >> 
 
> This makes sense - if we quench once the energy flow from
> primary-secondary has completed, but before it can reverse, then we'll
 >never see a secondary notch! A real poser is why the spectral splitting
 >also seems to go away... 

Certainly once the gap quenches, spectral splitting is gone, but I would
speculate that there is some spectral splitting occuring before the gap
quenches, even on first notch quench, but this splitting may not have time to
beat and re-beat with all the frequency and out of phase components that
occur during beating.  Thus with a slow or bad quench (and insufficient spark
loading to lower the Q), the beating and re-beating may get "out of hand"
(and out of the sec coil--as racing sparks)?

> > Happy coiling!
 > 
 >>    John Freau
  >>
>    --Bert--

John Freau