In article . net, robert casey
writes:

Someone inserted a carbon telephone microphone in
the feedline between the transmitter and antenna, and
produced a crude form of AM.

Actually, Reginald Fessenden did a lot more than that, as early as 1900. By
1906 he had two-way transatlantic *voice* radio communications working.

Couldn't have been
much power else the mic would have burnt up.

He got at least a kilowatt from one set.

These
mics vary in resistance along with the sound they hear.

Which is all an AM modulator really does.

Point is, there were folks using practical voice radio years before 1911. It's
all well documented. Of course that early voice equipment was more expensive,
less reliable and did not perform as well as its Morse code counterparts.

AM: 0%
Near but not = 0

Exactly!

Well, how far up did spark go?

Depends entirely on the design. In those days, the conventional wisdom was that
longer waves = longer distance, so there was little interest in going above
about 1 MHz.

No, *all* activity on radio was legal. Anything not specifically
outlawed is legal. The radio regulations came later.

There was *some* radio regulation in the USA as early as 1906. In the years
leading up to 1912, there were a number of bills introduced into Congress to
regulate radio even more. But there was no great urgency to enact any
comprehensive radio regulation until the Titanic disaster.

73 de Jim, N2EY