[Scan-DC] [OT]I wouldn't have believed it unless I'd seen it

[Shawnerz]

All,
Since there are a wide variety of people on this list,
maybe someone can explain this.
I'm over in Iraq doing some contract work.  We have a
Diamond discone atop our building attached to a PVC
pipe. The PVC pipe is tie-wrapped (or zip tied or
whatever you wish to call it) to another PVC pipe that
is anchored to our masonary/stone building.
We have a 50 ft. run of RG-8 coax connected to the
discone with N connectors.  At the shop end of the
coax, the N connector is adapted down to SMA male.
Early one evening about a month ago, we were all
sitting around the shop and we started hearing a
snapping/cracking noise.  About once or twice a
second, we'd hear, "Crack"  "Crack" "Crack"
After about 2 minutes, somebody said, what's that
noise?
We started looking around and saw there were arcs of
static electricity coming from the center pin of the
SMA connector going to the outisde shield at about a
once per second rate.
Fortunatly, the antenna wasn't connected to a receiver
at the time.
Then came the sand storm.

The question I cannot answer is, how did this happen?
I understand the preceeding a sand/dust storm, there
can be a highly charged electric field.  It happens
with regular rain/thunderstorms all of the time. 
Effectively, the antenna was isolated (ungrounded). 
If a large wave of highly charged particles hit the
antenna, it would have hit the top elements *as well
as* the bottom elements.  The difference of potential
*should have been* zero and there shouldn't have been
any arcing.  Obviously, this wasn't the case.
If the antenna was grounded (as it is now), the arcing
would make more sense.  The wave of charged particles
would hit the top elements of the antenna.  The bottom
elements would be at ground potential creating a
difference of potential, thus the arcs.
This wasn't the case since the antenna was attached to
a PVC pipe.
Any ideas anyone?
-Shawn



		
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