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Re: Primary dummy-loading

Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ludev-at-videotron.ca>

Hi Duncan, Gary, all 

Yes I think a resistive load could not react like a secondary;
when you have a secondary in place you normaly have transfer of
energy from the primary to the secondary and back to the primary
( if you don't have a streamer occuring ) and the streamer don't
necessarily happen at first notch. I doubt a resistive load could
give this kind of envelope. For certain test resistive load are
OK but it will not give you a right image of the reality. I
regret but I have no good idea of a way to emulated a secondary
in real condition ... may be other ?


Luc Benard

Tesla list wrote:
> Original poster: "Dr. Duncan Cadd by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>
> Hi Gary, All!
> >While I really can't be running my coil in my basement due to
> >streamer-strike concerns, I would like to be able to do some level of
> >live indoor testing to scope gap timing.  If I simply remove the
> >secondary, there can be no quench and the gap and cap activity will
> me
> >much more stressful than I'd like to impose on them.
> >
> >I was wondering if anyone has come up with a way to dissipate the
> bulk
> >of each primary bang in something less hazardous to my basement (and
> me
> >and my scope) than streamers.  I was thinking of either some kind of
> >dummy load resistor in series with the primary.  Or perhaps placing a
> >sheet of aluminum slightly above the primary to dissipate the bangs
> as
> >eddy currents?
> I think both of these will work, the eddy current load is particularly
> innovative, but I think your problem is going to be substituting a
> suitable load without changing the very quench/timing characteristics
> you want to measure.  That is going to be the tricky bit.  You can
> couple a resistive load (e.g. a "cantenna" - oil filled ham
> transmitter load) with the same coupling constant as the normal
> secondary which you can obviously determine in the usual way, but can
> you be sure that a purely resistive load produces the same quench &
> timing characteristics as the secondary when sparking, and what
> exactly is the right value of load resistance at that same coupling
> constant anyway?  Problems I have often mused on, with no useful
> outcome :-(
> I feel your best bet is to take the empirical approach and try
> connecting a variety of resistive loads, and maybe add a bit of
> inductive and/or capacitive reactance to the loads, and see if the
> quench & timing characteristics do vary according to the value of load
> resistance and reactance.  Maybe the variation will not be large, but
> this could be useful data to measure in any case, I'm sure someone on
> the list will appreciate it.  It's a moot point whether you can
> successfully equate this to a sparking secondary though.  The other
> option is to have a grounded rod close enough to the topload to ensure
> that all sparks go to the grounded rod and not the other items in your
> basement.  For scope protection I have used a small neon bulb directly
> across the probe, in parallel with a low value (1 ohm) resistor, and
> this seems to work quite well (and yes, the neon did light up with a 1
> ohm resistor across it :-)
> Hope this helps.
> Dunckx
> Geek#1113 (G-1)