Re: Streamer Growth

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

> >
> > only if you try and do it in a one shot measurement short pulse.  There
are
> > a variety of ways to get "superresolution imaging" at < wavelength (or
> > 1/bandwidth, roughly the same...), pretty much relying on a series of
> > measurements (all tied to power and bandwidth and time... that BT
product
> > thing..) Yes, there is an issue of coherence length and time for the
pulse
> > compression, but, there might be a way to back it out.  Think of speckle
> > processing on astronomical video to get superresolution.   I'm not
saying it
> > would be easy, or even practical, but the possibility of RF imaging the
"ion
> > cloud" around the topload is one that deserves some thought.
>
> I've read a bit about superresolution lately, but only in connection
> with coherent systems and a stable target.  Won't say it's impossible as
> I plain don't know, but the target we're trying to measure sure is
> neither stable or time stationary.  Furthermore, I suspect there is no
> well-defined thing to image on. A "simple" UWB system would probably
> come closed to working, but not simple to implement with the kind of
> "receiving" equipment (very wide-band scope) that most of us own.

And, the typical UWB radar actually uses a single sliding range gate that is
swept through the range (much like a sampling head on a fast microwave
oscilloscope)... all you need is a really fast switch (or more properly, a
reasonably fast, but very repeatable, switch), and, as you point out, a
stable target.

I was thinking that one might be able to approach the whole thing
statistically... You wouldn't be able to track any one streamer on any one
bang, but over thousands of streamers in a cloud, and over thousands of
bangs, there might be something to be learned from the statistics.

> Generating the transmit pulse is no big deal, but receiving the echoes
> sure is.   A few years back I did quite a bit of measuring with an
> "impulse radar" put together by some friends of mine.  The transmitter
> consisted of a back-biased rectifier diode pulsed into breakdown and
> mounted at the feed point of a large (4' square) flared-notch horn.
> Total input power to the diode was a couple of watts average.  The
> receiver was another similar horn hooked to the input of a very wide
> bandwidth Textronix "digital" scope. Ten thousand dollar transmitter,
> all in the purchased horn, but the scope was about 50 k as I remember.
> The system was sensitive enough to detect reflections from an Edison
> Company power line about a half mile away, particularly when the S/N was
> enhanced by averaging the signals from a number of different pulse
> receptions.  The bones of that thing are still around, but don't know
> where and don't think it could be ressurected.  If it were I think it
> would be useful for some of the measurements we're talking about.


You need to scrounge up an old sampling head...  The pulses could be cheaply
generated with, hmmm, a spark gap and a small capacitor..