Hello all,

I didn't know where else to post this, so I apologize if it doesn't
quite belong here.

I built a magnetic field listener a couple of weeks ago, it consists
of simply a lot of magnet wire wrapped around a steel spike nail, the
resulting coil fed into a series of low noise amplifiers and
ultimately a small speaker, headset, or recording device for
monitoring. It does a fine job at picking up electric motor noise, crt
noise (can pick up the degaussing field at 70' or more!), close radio
transimitters, stray fields emitted by signal or power cables, etc. It
will even make a neat "shash shash" sound if you waggle a permanent
magnet near the coil.

The first time I gave it a listen, I thought I'd found my elusive
solution for the perfect lightning detector, as the background seems
to always be chock full of lightning sferics. Checking at:

http://www.lightningstorm.com/tux/js...splay_free.jsp

I found that these sferics were still thickly present even as far away
as several hundred miles, and perhaps much further. Those of you that
have fooled with VLF radio, you know what a sferic sounds like, and
this sounds exactly like them. I had already packaged the receiver
circuits into a grounded metal can to eliminate radio wave reception,
so I finally decided I was picking up the *magnetic* fields generated
by the intense conducted power of the lightning bolts. This, I
reasoned, was proving easier for me to pick up than normal VLF radio
sferics because magnetic fields are less interrupted by objects like
trees, buildings, and the earth itself. The sferics I was hearing with
this magnetic listener are audible all day long as a sort of "frying"
lightning crackle sound, regardless of distance to the nearest storms,
and at night tend to stretch out into the *tweaks* so many VLF
enthusiasts are familiar with.

Since I seemingly found a great way to detect lightning, I just
assumed that this would make a badass relative lightning distance
monitor. So I waited for a thunderstorm to come into my area. Now this
is what I don't get: The lightning crackles get only somewhat louder
and clearer, even with extreme proximity (say 10 miles or less), to
the point that I can't really discriminate effectively between distant
strikes and close strikes. Additionally, the close lightning doesn't
have the normal "AM radio" sharp crackle to it, rather it sounds more
like a liquidy "puop" sound, something like the pop sounds a deep
fryer will make.

I've since put this project on hold, as currently I am seriously busy
with other things, but when I get time I will try to hook it to my
homebrew parallel port ADC and see if it can actually discriminate any
kind of strength difference between distant (100 miles) and close
(30 miles) lightning. At this point, I don't hold much hope, although
I will try, and I will keep this design for other uses and simple
entertainment as well since it is pretty neat to listen to whatever
magnetic fields come my way. I also think this might make a good
aurora listener, but haven't had the opportunity to test that idea
yet.

Anyways, I've rambled enough. Thanks to any of you that can lend some
ideas and opinions about this thing!

- NR



"The usual approach of science of constructing a mathematical
model cannot answer the questions of why there should be a
universe for the model to describe. Why does the universe go
to all the bother of existing?"

- Stephen Hawking

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