On Aug 6, 8:21 am, "Tam" wrote:
"K7ITM" wrote in message

...

On Aug 5, 7:31 pm, "Walter Maxwell" wrote:
Do really believe that there was a transmitter in the 1920's that could
deliver
500 kw?. The first station that could come up with that amount of power
was in
the 1930's,W8XO, the experimental station of Powell Crosley, that became
WLW
again when the experimental period was over. Are you aware of the
technical
difficulties that obtained in just getting that monster to work? General
Electric and Westinghouse supplied most of the parts, the rest by RCA,
and RCA
was the company that strived and strived before it was workable at that
power
level. I once worked for Harold Vance, the RCA engineer in charge of the
project. Certainly this didn't happen in the 1920's, and not in
Schenectady.
Somebody's been
feeding you horse hockey.

Walt, W2DU

On the other hand, there were spark transmitters well before that in a
similar power class. As I understand it, the powers actually achieved
as output were often either not well known or were kept quiet for
various reasons, but they were clearly in excess of 100kW. Apparently
the Oct. 1920 issue of "General Electric Review has an article by
Alexanderson about a 200kW alternator-driven transmitter. I
understand that there were also some high-powered (Poulsen) arc
transmitters (quite distinct from the shock-excitation of spark). I
found one reference to a Poulsen arc transmitter that ran at 3.6 MW
input power which was "still active in the early 1920s..." It ran on
~50kHz. Pretty much all this early stuff was below 100kHz, which of
course yields very reliable propagation if you put enough power into
it.

But WLW ran 500KW of 100% AM modulation. I understand just the modulation
transformer was the size of a room in order to handle the 250 KW of audio. I
believe it was on 700 KHz. See the link I gave above.

Well, admittedly I was taking it a bit out of context, but my posting
was a response to Walter's "Do really believe that there was a
transmitter in the 1920's that could deliver
500 kw?" And the answer is, yes, I do. Maybe not valve-based, but
more than one transmitter, and capable of modulation as well:
apparently Poulsen arc transmitters were FSK, since they couldn't be
keyed on and off. And apparently the alternator based transmitters
could be keyed at up to 100wpm. I'm pretty impressed with what the
radio engineers of that era were able to achieve.

Cheers,
Tom

K7ITM wrote:
.. See the link I gave above.

Well, admittedly I was taking it a bit out of context, but my posting
was a response to Walter's "Do really believe that there was a
transmitter in the 1920's that could deliver
500 kw?"

I think the operative word here is "deliver", by which I would mean
"radiated into the far field". Dissipating half a megawatt in the
system is impressive, but not necessarily as a transmitter.


And the answer is, yes, I do. Maybe not valve-based, but
more than one transmitter, and capable of modulation as well:
apparently Poulsen arc transmitters were FSK, since they couldn't be
keyed on and off.

One scheme was to change the resonant frequency of the antenna (via taps
on a coil), which was the frequency determining part of the system, the
arc providing a negative resistance characteristic for making an oscillator.

And apparently the alternator based transmitters
could be keyed at up to 100wpm. I'm pretty impressed with what the
radio engineers of that era were able to achieve.

It IS very impressive, but whether they could *radiate* half a megawatt
is sort of a good question.

Consider for comparison the ELF transmitters in Michigan..several
Megawatts to radiate less than 10 Watts

Or Project Sanguine, which was soemthing like 800 MW to radiate a few watts.


I know of several Tesla coils that have average power inputs in the
hundreds of kW range, but they don't radiate a whole lot, even with 20+
meter sparks as an antenna.



Cheers,
Tom