On Apr 25, 4:16 pm, Paul Keinanen wrote:
On 25 Apr 2010 14:57:32 -0400, (Scott Dorsey) wrote:

The Alexanderson puts out a very nice note.... the problem with it is keeping
it on frequency, not phase noise. Oh, also keeping it from flying apart and
exploding is another issue. It's a far higher tech device and much more
difficult to make... and also not so effective at higher frequencies.

There is still one functional station (operated one day each year)http://en.wikipedia.org/wiki/Grimeton_VLF_transmitter

Hey OM:
From:
http://en.wikipedia.org/wiki/Alexanderson_alternator

"Because of the limits of the number of poles and rotational speed of
a machine, the Alexanderson alternator is at most capable of
transmission in the lower mediumwave band, with shortwave and upper
bands being physically impossible."

Says it all?
73 OM
de n8zu

raypsi wrote:
Hey OM:
From:
http://en.wikipedia.org/wiki/Alexanderson_alternator

"Because of the limits of the number of poles and rotational speed of
a machine, the Alexanderson alternator is at most capable of
transmission in the lower mediumwave band, with shortwave and upper
bands being physically impossible."

Says it all?

The number of poles is part of the issue, but you'd think with modern
machining technology you could make a big rotor with maybe a thousand
poles. Problem is that if you do this, the capacitance kills you.

One possibility to run an Alexanderson alternator would be to run it
into a nonlinear device and then select one harmonic out. Again, it's
very inefficient....
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."