I have a neodymium magnet ELF-ULF transmitter in storage. I built it out of 
curiosity. Even the container is a curious thing, made to withstand the 
inevitable; pre-construction analysis showed that the radiated energy would 
transition from electromagnetic to kinetic by mid-ULF. The single (large) 
low-aspect-ratio magnet allows unambiguous evaluation of some nuances of near 
fields that might not be unambiguous with a coil. Mostly it's for the sake of 
curiosity and fun (strong sub-sonic/acoustic signatures), but being disinclined 
to metaphysical challenges I now leave it in permanent storage.

The above engenders much respect for the Alexanderson design.

Stefan's point well taken (in conjunction with note from Peter); voltage is an 
unavoidable critical constraint; the ERP of an Alexanderson design would be 
mechanically limited with an ultra-short antenna, but the critical limit on ERP 
would be imposed by voltage; a mechanically modulated dielectric or 
ferroelectric source (ref Peter and Stefan) would need, politely speaking, low 
loss and high density to mitigate the voltage constraint.

73,

Jim      


  

-----Original Message-----
From: [email protected] 
[mailto:[email protected]] On Behalf Of Warren Ziegler
Sent: Wednesday, December 21, 2016 11:34 AM
To: rsgb_lf_group
Subject: LF: Re: LF: Re: LF: Re: LF: ULF experiment: A MEchanical Based Antenna​

Hi John,

  I went to the M.I.T. library and made copies of Alexanderson's original 
papers and did some other research beyond that. The Alexanderson alternators 
were good up to about 20kHz, they achieved higher frequencies by feeding the 
output of the alternator into a saturated reactor which generated harmonics, 
they then filtered out the harmonic that they wanted and fed it to the antenna. 
Not sure but the antennas were of such high Q that additional filtering might 
not have been necessary. They would indeed fly apart if they tried to generate 
a 100kHz fundamental directly from the alternator!

About 15 years ago, I led a group trying to make high-speed energy storage 
flywheels, they rotated about 45,000 rpm. Initial attempts to use mechanical 
bearings mounted in  a springy steel housing were a failure, magnetic bearings 
(with a dsp based controller) were absolutely necessary to get through the 
various mechanical resonances.

I made a trip to see British Nuclear Fuels in the U.K.,  they did make a 
technically  successful high speed energy storage flywheel, but it flopped 
commercially since it was too expensive to make for the intended markets.

A group of Aero engineers at M.I.T. tried to make microturbines with dime sized 
rotors etched out of silicon or silicon carbide, they hope was to have a small 
power generation source that would operate from a gaseous fuel and replace 
batteries. The M.I.T. turbines would spin at over 100,000 rpm and generate A.C. 
(R.F.) at 3 to  4 MHz!  I met with Alan Epstein  and his group at M.I.T. back 
in the early 2000's  he detailed some of the problems they were having. I 
believe the project was ultimately abandoned.



73 Warren

On Wed, Dec 21, 2016 at 10:41 AM, John Rabson <[email protected]> wrote:
> Alexanderson generators were built for frequencies up to 100 kHz and did not 
> display a tendency to fly apart. For background information on the 17.2 kHz 
> installation see CREGJ 96.
>
> John F5VLF
>
>> On 21 Dec 2016, at 13:54, Martin Evans <[email protected]> wrote:
>>
>>
>> Ah yes- of course Andy.
>>
>> Better stand well back when I try it then!
>>
>> Martin  GW3UCJ.
>>
>>
>>
>>
>>> 8000 * 60  = 480000 RPM
>>>
>>> 'jnt
>>>
>>>
>>> On 21 December 2016 at 12:42, Martin Evans <[email protected]> 
>>> wrote:
>>>
>>> Forgive me for asking what may be quite obvious to many - but does this 
>>> mean that if I spun a magnet at 8000rpm then I would generate a 8kHz radio 
>>> signal, identical in every way to an 8kHz signal generated in a more 
>>> conventional manner?
>>>
>>> If so, it sounds a lot easier than winding all that wire.....until the 
>>> magnet flew apart anyway!
>>>
>>> Martin  GW3UCJ  Swansea.
>>>
>>>>
>>>> ever heard of a "A MEchanical Based Antenna" ?
>>>>
>>>> Me neither until today ;-)
>>>>
>>>> 73, Rik  ON7YD - OR7T
>>>>
>>>>
>>>
>>>
>>
>
> [email protected]
>
> Researching history of RABSON, BLACKSHAW, GAUNTLETT, VERLANDER and 
> ROBSONNE
>
>
>
>
>



--
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1