Re: Buzzer tuning question

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

Original poster: "Ed Phillips by way of Terry Fritz <teslalist-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
 >
 > Original poster: "J. B. Weazle McCreath by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <weazle-at-hurontel.on.ca>
 >
 > Hello Coilers,
 >
 > In searching the archieves for info about "tuning buzzers" I found one
 > message stating that a buzzer can be used to excite the primary so you
 > can find the tap point with low power.  It was suggested that a 'scope
 > would detect the secondary field, and you would simply tap for maximum
 > output.  Not having a 'scope, I wondered if a high impedence R.F. volt
 > meter could be used to measure the voltage developed on the secondary?
 > Has anyone tried this, and if so what did you use?
 >
 > 73, Weazle, VE3EAR/VE3WZL
 >
 > "Don't take life so seriously, nobody has survived it yet!"
 >
 > Listening: 7,055, 147.030+, and 442.075+
 > http://www.hurontel.on.ca/~weazle


	I think I'm the one who posted that message; at least I posted a
similar one.  The high-Z meter might work, but you can't bring the leads
close enough to the top terminal of the TC or you'll detune it badly.
When I used the scope I hooked the vertical axis to a small piece of
aluminum plate (~1" x ~2"), set the gain to max, and then adjusted the
distance for more or less full-scale deflection at resonance.  (The
ground side of the scope went to the bottom of the coil, of course.)
The buzzer method certainly will work, and a high-enough powered buzzer
would give useful sparks.  During WW1 there were some 100 watt "buzzer
transmitters" used which had a similar configuration.  Many signal
generators used the same circuit and I have a General Radio 174-B
wavemeter (circa 1922) which does the same thing.  Tunes from about 100
kHz (3000 meters) to 1500 kHz (1500 kHz) and produces a signal which is
heard easily with a broadcast receiver.

	As for your VM, I'd try this idea with the small plate (you pick the
size).  The problem will be that if you're anywhere near a BC stations
you may pick up the voltage from it and not see the TC output; with a
scope it's easy to observe what you're looking at, but with the VM it
would be harder.  Another possibility is a neon bulb, but you may not
get enough voltage to excite it.

	The experiment is easy, so give it a try.  Notice that the primary
capacitor and coil IN SERIES are connected across the interruptor points
of the buzzer.

Ed