To: rsgb_lf_group@blacksheep.org
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From: =?UTF-8?Q?Wolfgang_B=c3=bcscher?= <dl4yhf@freenet.de>
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Date: Wed, 16 Jan 2019 20:33:50 +0100
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Subject: Re: ***SPAM***Re: VLF: GOTA
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Hello Jim,

Of course the "20 meter long tube" wasn't a serious suggestion. I 
wouldn't "seriously" transmit there anyway, and you are right, it will 
not "radiate" more than a few femto-femtowatts (not sure what the proper 
tech prefix would be). The larger / longer the structure, the better (I 
think) and if you manage to place such a beast between two skyscrapers 
with massive steel construction (so the mag field has something to 
couple into), the signal may even be detectable a bit further way.

Similar like yourself, I have tied a couple of bar magnets to an 
electric motor (from a cassette tape deck, with mechanic RPM 
stabilisation built inside) and was pleased to detect it over 50 meters 
away. But not good enough for a ground-penetrating 'beacon system' for 
caving, which was one of my hobbies in days long gone by.

If we'd compare this with a ferrite bar antenna, length (of the magnet 
or bar) would be more important than thickness.

73,
   Wolf DL4YHF .


On 14.01.2019 22:14, hvanesce@comcast.net wrote:
> 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: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Wolfgang Büscher
> Sent: Sunday, January 13, 2019 5:58 AM
> To: rsgb_lf_group@blacksheep.org
> 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:
> ...
>
>
>