Editing Reginald Fessenden (section)

===Alternator-transmitter===
Fessenden's ultimate plan for an audio-capable transmitter was to take a basic electrical [[alternator]], which normally rotated at speeds that produced alternating current of at most a few hundred cycles-per-second ([[hertz|Hz]]), and greatly increase its rotational speed, in order to create electrical currents of tens-of-thousands of cycles-per-second (kHz), thus producing a steady continuous-wave transmission when connected to an aerial. However, it would take many years of expensive development before even a prototype alternator-transmitter would be ready, and a few years beyond that for high-power versions to become available. One concern was whether at these high speeds the alternator might disintegrate due to the high rotation speed tearing it apart. Because of this, as a precaution, while the alternator was being initially developed it was "placed in a pit surrounded by sandbags".<ref>Aitken (1985), p. 69.</ref>

Fessenden contracted with [[General Electric]] (GE) to help design and produce a series of high-frequency alternator-transmitters. In 1903, [[Charles Proteus Steinmetz]] of GE delivered a 10&nbsp;kHz version which proved of limited use and could not be directly used as a radio transmitter. Fessenden's request for a faster, more powerful unit was assigned to [[Ernst Alexanderson|Ernst F. W. Alexanderson]], who in August 1906 delivered an improved model which operated at a transmitting frequency of approximately 50&nbsp;kHz, although with far less power than Fessenden's rotary-spark transmitters.<ref>The Brant Rock rotary-spark transmitter was rated at 100,000 watts ([https://babel.hathitrust.org/cgi/pt?id=uiug.30112008072784&view=1up&seq=787 "Some Interesting Radio History"], ''Radio World'', September 8, 1923, p. 21), while the alternator transmitter had an estimated output of 12 watts (Aitken (1985) p. 74).</ref>

The alternator-transmitter achieved the goal of transmitting quality audio signals, but the lack of any way to amplify the signals meant they were somewhat weak. On December 21, 1906, Fessenden made an extensive demonstration of the new alternator-transmitter at Brant Rock, showing its utility for point-to-point wireless telephony, including interconnecting his stations to the wire telephone network. As part of the demonstration, speech was transmitted 18 kilometers (11 miles) to a listening site at Plymouth, Massachusetts. A detailed review of this demonstration appeared in ''The American Telephone Journal''<ref name="experiments" /> and a summary by Fessenden appeared in ''Scientific American''.<ref>[https://babel.hathitrust.org/cgi/pt?id=pst.000062999960&view=1up&seq=76 "Recent Progress in Wireless Telephony"] by Reginald A. Fessenden, ''Scientific American'', January 19, 1907, pp. 68–69.</ref> A portion of a report produced by [[Greenleaf Whittier Pickard|Greenleaf W. Pickard]] of the Telephone Company's Boston office, which includes additional information on some still existing defects, appeared in [[Ernst Ruhmer]]'s ''Wireless Telephony in Theory and Practice''.<ref>[https://babel.hathitrust.org/cgi/pt?id=uc1.$b33006&view=1up&seq=229 "Wireless Telephone Tests at Brant Rock and Plymouth, Mass."] by Greenleaf W. Pickard, included as an appendix in ''Wireless Telephony in Theory and Practice'' by Ernst Ruhmer (translated from the German by James Erskine-Murray), 1908, pp. 205–214.</ref>

Although primarily designed for transmissions spanning a few kilometers, on a couple of occasions the test Brant Rock audio transmissions were apparently overheard by NESCO employee James C. Armor across the Atlantic at the [[Machrihanish]] site.<ref>[https://babel.hathitrust.org/cgi/pt?q1=transatlantic;id=pst.000063000184&view=1up&seq=187" The First Transatlantic Telephonic Transmission"] (correspondence from Reginald Fessenden), ''Scientific American'', September 7, 1918, p. 189.</ref>