60 Gaps at 4 mil Data (fwd)
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Date: Fri, 10 Jul 1998 15:53:31 -0600
Subject: 60 Gaps at 4 mil Data
I was finally able to get my 60 gap, by 4 mil spacing, spark gap put
together. It's quenching was better than my 7 mil gap but not by any great
amount. My old gap (7 mil) gave good quenching with a coupling of 0.1242.
The 4 mil gap goes to 0.1475. With breakout, it will go to 0.1753 for a
first notch quench. So it is better, but not by any giant degree. The is a
picture of the 4 mil spark gap at:
It has 60, 2 inch long, 1/2 inch copper pipe sections epoxied to an oak base
in two rows. I used 4.0 mil paper strips to space the sections while the
epoxy cured. I simply placed a section of pipe across the two rows to
adjust the voltage.
I also measured the firing voltages as follows:
Note that I live 5500 feet above sea level so the voltage will vary somewhat
Gaps Peak Volts Volts/mil
2 1810 226
4 3648 228
6 5091 212
8 6137 192
10 6449 161
12 7354* 153
14 8994 161
16 9871 154
*This was the same as 7 gaps at 7 mil or 3 gaps at 24 mil. But that
probably varies much.
It is not quite linear but I could hear corona starting up and such as I
raised the voltage which probably affects the firing voltages much. It
looks like the voltage evens out to about 157 volts/mil or 630 volts per
gap. At see level, that would be about 600 volts/gap.
This gap is very quite. The coil is much louder than the gap. The light
from the gap was also very low. It was very easy to have the gap uncovered
without noticing noise or light from it. Very pleasant to work around!
I also noticed that the gap was extremely stable. When it was firing, the
coil waveforms were rock solid. There was almost no jitter or the usual
unstable character to the output. This was very noticeable on the scope. I
immediately noticed the waveform's increased stability when I first powered
I seemed to run very cool. After 30 seconds of running, the copper was
still cool to the touch. Barely warmer than before the run. I had no fan
or any other cooling. However, this was with first notch quench which is
very important for cool gap running.
I really like this gap's ability to very easily change the gap voltage. I
ran two rows of gap tubes and I simply lay another tube across the rows for
voltage tapping (see picture on above web page).
I really like this new gap. It doesn't seem to want to clog up so far but
it would be very easy to clean if it did. I probably don't need all 60 gaps
but I didn't know before I build it. It cost be about $15 and took about 4
hours to make.
So far this is the best gap I have built by far, especially for the research
stuff I do.