Re: single shot
Subject: Re: single shot
From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Date: Mon, 20 Nov 1995 10:38:46 +1200
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Here are some further thoughts on this. There is an
interesting experiment you can do in single (or better, SLOW
repetitive) shot mode that highlights the transmission line
characteristics of the secondary very well. The experiment is
rendered even more dramatic if the secondary has a sufficiently
large terminal to prevent sparks breaking out in single-shot
mode (it must of course be correctly tuned to the primary).
Start firing the coil. Now gradually move a discharge rod
connected to the secondary ground towards the secondary terminal while
observing the gap discharge. The gap discharge brilliance will reach
a minimum when the the rod is close enough to draw thick sparks.
At this point, energy absorption and spark dissipation by the
secondary is at maximum with a minimum of energy being reflected
back into the primary. Moving the rod right up to the terminal
causes the gap discharge to brighten again.
The point at which the gap is least bright is when the sparks
to the discharge rod are loading the secondary such that the load
matches the secondary characteristic impedance. This is classic
transmission line behaviour. Too light or too heavy loading
causes more energy to be dissipated in the primary circuit.
A thought following on from this re the equal Q dilemma -
secondary Q drops when it is loaded so it will tend towards the
primary Q anyway, particularly when the secondary discharge
path is well ionized as in normal operation.