English: A portable military wireless station in 1922, operated by members of the 101st Signal Battalion, 2nd Corps, US National Guard Signal Corps, on field training near Peekskill, New York. Two guardsmen crank a hand-powered electric generator (left) as a third (center) operates an early vacuum tube transmitter sending text messages in Morse code using a telegraph key. The source (p. 58) says the equipment is an SCR-99, which can transmit on wavelengths between 900 m (330 kHz) and 1500 m (200 kHz). It uses VT-1 triodes for receiving and VT-2 triodes for transmitting, and has a range of about 100 miles with 320 V on the transmitting tubes.

Caption: TRANSMITTING IN THE FIELD: The power for operating this equipment is furnished by the hand generator. Note the collapsible metal mast that serves as a support for an umbrella antenna

Alterations to image: removed caption text from background.