Hello Wolf,

If I am treading on anyone's intellectual property please advise. 
Years ago I built a version of what you mentioned, and I don't operate it
often because of fear of kinetic effects :-) 
The stack of 3" diameter 1.5" thick magnets is epoxy encapsulated and
rotates at 20 Hz inside of an enclosure with three 1/2" thick cabinet-grade
plywood walls on all six sides of the enclosure. It is designed for several
orders of magnitude safety margin against kinetic effects.
It's lots of fun but I wouldn?t recommend it to anyone without access to
lots of sandbags.

I have a question:
I did not strive for a high aspect ratio (I did not strive for a tube that
is long compared to diameter) on the basis that at 1 Hz to 20 Hz the far
field is irrelevant to most of us, and in the near field, only the volume of
a good neodymium magnet matters:

B  = (B_of_magnet x volume_of_magnet)/(2  x  pi  x  r^3)  

Does this seem right? Size matters but length doesn't?

On a related topic, I don't want to contradict your thought below, but I
don't think that a 1.6 Hz transmitter that has the range of an ELF
guard-rail transmitter would be made with magnets; because:
To have such a range, a 1.6 Hz experimenter would technically need to file
for human-subjects authorization unless the magnetic device was operated in
the wilderness, but we read in this thread that the 1.6 Hz device is safe
and convenient to use.

73,

Jim AA5BW
    
  

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Wolfgang Büscher
Sent: Sunday, January 13, 2019 5:58 AM
To: [email protected]
Subject: Re: ***SPAM***Re: VLF: GOTA

Claudio - just wait until that b.s.-meter pulsates 1.6 times per second :o)

20 meter long tube filled with neodym power magnets, rotating at 96 RPM...
but now we'll never get to know this top-secret technology. Harr harr.

On 13.01.2019 10:59, Claudio Pozzi wrote:
...