Jumping in with both feet?
From: SBJohnston-at-aol-dot-com [SMTP:SBJohnston-at-aol-dot-com]
Sent: Thursday, January 29, 1998 4:35 PM
Subject: re: Jumping in with both feet?
Well, I've rolled my "dead man's coil" out into the driveway and I'm ready to
crank it up. I'll record the results here as I go...
With just the bolt protruding out of the ceramic top insulator, full 11 turns
on the primary, and the spark gap set to 0.100 inch, I had a couple inches of
tiny, but lovely, corona discharge at about 50% on the variac. Any higher
on the input voltage and the top wires of the secondary began to flash.
Dropping to the 9-turn tap on the primary (should be better tuned with my
four caps in parallel) dramatically increased the discharge from the bolt, as
well as the tendency for the top wires to discharge for the same variac
Widening the spark gap greatly increased the size of the discharge, but also
changed its character from a continuous sizzle to a rythmic snapping. Best
performance seemed to be at about 0.250 inches gap. Hmmm....seems wide...
I'm surprised at the loudness of the sound, particularly when the gap is wide
and the snaps are more distinct. Then again, I've always been surprised when
I've heard a high voltage zap in one of my transmitters (of course, none of
the those were desired, and usually involved the destruction of some
I tried the 6"x8" metal dome top-load but it seemed to suppress the
discharge. Perhaps that's normal - maybe if it had a nearby object to flash
I then tried about 8" of solid wire pointing straight up. WOW! What a
display! The sharp point concentrated the discharge nicely, resulting in a
beautiful round ball of streamers about 15-24" in diameter depending on input
E. At about 75% on the variac it was up to 30" diameter but the top wires of
the secondary were beginning to join in.
At this point I notice the neighbors are beginning to come to their
Next I brought the tip of a grounded 8' aluminum antenna element into the
near field - and was rewarded with 24" solid strikes instead of the corona
discharge. It was interesting to see how the voltage builds, then POW,
builds then POW, builds then POW, builds then POW.
Now the neighbors are out of their houses and coming toward me. I don't see
any pitchforks or torches, but still... Should I pretend I know nothing:
"What sparks? I was just cleaning out the garage. Oh, that old thing?
No, no, it couldn't have been doing that".
No, I didn't have to face them -- they were just setting out their garbage
cans. Well, I'm sure they were trying to get a closer look at what I'm up
That's enough excitment for tonight. I guess my next step is to construct a
toroidal discharge terminal. Am I right in thinking that it will increase
the buildup of voltage prior to discharge? Will it suppress streamers in
favor of arcs/strikes? I need to read more... off to the archives.
I guess my next