Electrical World, August 10, 1907, pages 293-294:
Reporting Yacht Races by Wireless Telephony.
The first actual application of radio-telephony to practical work anywhere in the world was made at Put-in-Bay, in Lake Erie, during the week of July 15 to 20, in reporting the regatta of the Interlake Association. The Radio Telephone Company installed the De Forest wireless telephone on board of the cruiser yacht "Thelma," and also equipped a shore station at the Fox Dock at Put-in-Bay.
The "Thelma" followed the competing yachts around the course through most of the races and full and graphic accounts were telephoned into the shore station.
The greatest distance at which the reports from the yachts were heard and recorded was four miles, considered remarkable in view of the height of "Thelma's" spars and the power of the transmitter on board. Her equipment comprised a 220-volt generator of 1 kilowatt capacity, the DeForest oscillator and transmitter, and for the receiving apparatus an audion detector and "pan cake" form of syntonizer or tuner. Her aerial wires led through the roof of the wheelhouse to a small crossarm on top of the foremast and thence to a similar arm on the mainmast. Ground connection was at first made to the propeller shafts of her twin screws, but as this was found insufficient, more area was added by fastening two sheets of zinc to the yacht's hull at the bow.
The telephone dynamo was belted direct to the flywheel of her starboard engines, aft, and the rest of the radio apparatus was mounted on a small table in her main cabin convenient to all.
On shore 110-volt direct-current was available and this was transformed to 220 volts by a motor generator. The current was led through a rheostat and choke coils to the oscillator. Connected to this oscillator is a shunt circuit consisting of a condenser of peculiar construction and a primary coil, the exact number of turns of which could be varied at will to alter the tune or wave length of the electrical waves which were generated. A second coil within this primary had its upper end connected direct with the antennae or aerial wire, while its lower end led first through the microphone transmitter and thence to the earth plate. In this way the changes in resistance in the microphone produced by the modulations of the human voice directly affect the intensity of the high-frequency currents which are continually passing from the air wire to the ground plate. Inasmuch as the receiver instrument is affected exactly in proportion with the strength of the received electric waves, it is evident that every variation in the microphone resistance by the voice will be reproduced to the listening ear at the distant station by the vibration of the telephone diaphragm there. The microphone transmitter and the telephone receiver are exactly the same as used in the wire telephone, with which all are familiar. The "oscillator" and the "responder" are the only new and additional features, and the ether takes the place of the connecting wire.
Upon the finish of the regatta the telephone apparatus from the "Thelma" and the Put-in-Bay shore station was shipped to Toledo, where it is the intention of the Radio Telephone Company to install it permanently, where it can be in communication with other wireless telephone sets to be installed on vessels sailing Lake Erie. The Great Lakes offer, perhaps, the most promising field anywhere in the world for the first general application of this new invention to the needs of a merchant marine, and it is the intention of the company to at once enter this promising field.