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RE: Plane wave antenna thoughts



Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Marco,

So the streamers ionize the air and add a dynamic boundary condition to the electrostatics between the topload and antenna.... I cannot immediately confirm or deny that...

One would need to look at the situation on say a digital scope that could capture over say one second. Then any net charge effects and the associated attenuation or distortion of the signals would be apparent. Or, one could set up a known HVAC signal from say and NST and see if a nearby running coil affected that reading. I wonder if the coil's power would simply push the ion cloud away since the impedance of the cloud would be high and it would not be able to supply much current to fight the coil's much higher available secondary current.

A simple JFET op-amp voltage follower could raise the impedance of the probe to say 1000M ohms for a low cutoff frequency of 0.007Hz. But then one would need a way to discharge or zero it. It would also then be vulnerable to all the goofy, odd, and weird errors and strangeness that affects electrometers in general. One would have to be very careful about what the signals really are.

I happily remember the usual visits from the safety department guy with those hand held ESD meters warning us that all the grounded lab equipment was at 20,000 volts!!!! Oh my!!!! Of course, we simply told them that the equipment was at ground and "he" was charged to 20,000 volts and he should not be holding the meter or he might break it :o))) He quickly scurry away never to be heard from again.... We later learned that he did end up blowing out the $400 meter...

Another problem would be if a sudden drop in the voltage reading was from a passing cloud discharging 1,000,000 joules 5 miles away, or from a 1nC fly landing on the antenna directly. The reading is the same...

So I somewhat "fear" electrometer measurements. There are so many things they might read for so many complex reasons... The chance of getting it "right" is pretty low...

Stork mentioned that Richard's meter was not working right. A flake of dust inside it could have caused that error. Or, a discharge may have damaged the amplifier capacitive input's insulators.... So much can go wrong.... And that is before and "scale" errors are considered!!!

We were thinking of telling the safety guy that are equipment grounds were really at 12475 volts next time and that he should send his meter in for repair or calibration. We figured that would get ride of him for two more months >:o))

We did try "once" to explain to him that the equipment was connected to a foot wide 100 mil strip of copper that went 20 feet into the ground and that nothing could go wrong with the grounding to the extent he was measuring... But he thought we were trying to trick him...

Cheers,

        Terry




At 03:46 AM 12/30/2005, you wrote:
Hi Terry,

My intention was really not to criticize your design. I several times
thought to build myself an antenna like yours, following your planes. I was
just speculating about the validity of the calibration.

> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Friday, December 30, 2005 10:47
> To: tesla@xxxxxxxxxx
> Subject: Plane wave antenna thoughts
>
> Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Space Charge - All that DC stuff ;-))  We can raise the lower
> frequency response easily enough if the space charge effects seem
> important...  But I don't think those effects have the Power or
> Energy to effect things much.  The system's frequency response (scope
> too!) tends to drastically discount such effects.  If the scope's
> input were buffered to say 1G ohm, then all that 0.1Hz stuff would be
> very apparent(!)...

What I'm talking about here is this (what follows is a simplified
explanation).
Your make a bang and it will leave a space charge where the streamer has
been extending (in air). That charge alters your Efield distribution
actually leaving a static Efield that your antenna probe cannot detect. The
charge eventually dies down but it takes several tenths of milliseconds to
do so. In the mean time, if you emit another bang the total Efield will be
well different from the one of the first bang. So, as your potential
estimations are based on the Efield, you'll commit a sensible error.

We could still speculate that the antenna is sensible to Efield
*variations*, not to offsets. But the problem, IMHO, is that the Efield
offset left by the previous bang alters much the environment where the
second bang will perform.

I have myself (last year) collected statistical bang data and noticed
clearly that previous bangs facilitate following ones to reach a given
target. The only way to get consistent measurements is to wait at least 20
seconds between bangs.

> Streamer effects - worst case - streamer hits the antenna
> =:O  Massive errors are noted!!!  Don't do that!! :o))  Streamers are
> dynamic and sort on unpredictable "noise" in the antenna's
> pickup.  Perhaps one could simply do digital averaging to "eliminate"
> their effects.  But "I" think if you have sort of small streamers
> directed far away from the antenna, it is not a "big deal".  I also
> thing "streamer loading (to the air) is not a "great" load on the
> coil anyway...  Or spice coil models would fail drastically if they
> were that far off...  It really depends on how accurate you are
> trying to be...  In many cases, like 50% if really good ;-))

Forget about streamer hitting the antenna. Image your antenna is on the side
of the discharge (the streamer is not incident). If you are near the leader
(the toroid) you'll measure 1. If you are near the leader tip, you'll
measure 60. Near to the streamer umbrella you could read 5. In other
positions I have no idea. And these "positions" are also changing with time.
And from bang to bang...
That's why I prefer measurements taken with no streamers (and with your
antenna, why not?) when trying to estimate the TC top voltage.

Best Regards