"Scott Dorsey" wrote in message
...
The Eternal Squire wrote:
Now I have a wiper that is laid across the edge of the
disk to make or
break contact with the outside of the star pattern, with
12 Volts DC
potential on the wiper. Assuming the shaft was
conductive and made
firm contact with the center of the star pattern, should I
see a 10
Mhz
square wave, suitable for say a switching mixer?

Question: How bad are the phase noise and harmonics
likely to be?

Really bad, but the harmonics you can filter. Phase noise
is going to
be way too high for anything but CW and your frequency
stability won't
be anything to write home about. However, the system you
describe was
built by Federal Electric in the 1920s, so it's at least
practical.
--scott

I think Federal used the Poulsen arc converter, a
steady arc where this thing is more closely related to the
rotary arc, also used in early wireless. There were two
types of rotary arcs but both operated at much lower
interuption rates, typically at around 400 hz, and generated
the RF energy by means of tuned tank circuits. Federal
Telegraph held Poulsen patents and exploited them in series
of wireless telegraph stations mostly on the West coast of
the USA. The rotary arc is not to be confused with the
Alexanderson alternator, a mechanical generator of low RF
energy. The alternator put out fairly pure CW. The
Alexanderson patents were controlled by General Electric and
were one of the main reasons for the founding of RCA after
WW-1, that is, to maintain wireless in the US under US
control.
The Poulsen arc was widely used on board ships. The
device requires an atmosphere of hydrogen for the arc and
has a supply of alcohol to provide the gas by means of
disociation due to the arc. That gave the radio operator a
supply of drinkable alcohol which made the "sparks" popular.



--
Richard Knoppow
Los Angeles
WB6KBL