RE: Plane wave antenna thoughts

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Marco Denicolai" <marco.denicolai@xxxxxxxxxx>

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