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RE: Frequecy counter, measuring 2ndary output

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Hi Jonathan:

Unfortunately, frequency counters of any vintage are useless for
directly measuring the frequency of an OPERATING Tesla coil.  The only
way to use them is to excite the base of your secondary with a signal
generator (Terry posted the plans for a very low cost DIY unit on his
web site*), measure the resonance peak with either a scope or the LED in
Terry's unit, and read off the frequency with your counter.  But this
won't take into account the low frequency shift that occurs in an
operating coil due to streamer loading.  The problem is that frequency
counters require the source to be oscillating at a given frequency
CONSTANTLY.  But in a spark gap type TC, the primary and secondary are
only active for less than 1% of the time.  Trying to measure that will
result in nonsense readings.

Trying to measure the BPS is a more difficult task.  I've also asked but
found no way to directly measure this with a counter.  The best way is
to use a single-sweep storage or digital scope.  Lacking that, Richie
Burnette has used an audio tape recorder to record the gap sound, then
played that into his PC's audio recorder.  This allows the ampitude
peaks to be seen and counted over some interval of time, thereby
indicating the BPS.  Haven't tried this myself but sounds simple enough.

Regards, Gary Lau


Original poster: "Jonathan Peakall by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jpeakall-at-mcn-dot-org>

Howdy all,

I was given a Sabtronics (ancient) frequency counter the other day, and
am wondering how I can use this to measure my secondary output
frequency. It is rated for 150v RMS, and so if I used two HV probes in
series, and my voltage is somewhere around 250kv, that should be reduced
to 25v, as both are 100:1 probes. If I just lay the probes somewhere out
of direct strike range, should I be able to measure my secondary output
without destroying the frequency counter?

What type of equipment is needed to determine the BPS of my tank? I was
also given a 1956 Heathkit 'scope, which lights up, but I haven't
checked yet. Can I use either it or the frequency counter?


Jonathan Peakall