WWV is a shortwave radio station, located near Fort Collins, Colorado. It has broadcast a continuous time signal since 1945, and implements United States government frequency standards, with transmitters operating on 2.5, 5, 10, 15, and 20 MHz. WWV is operated by the U.S. National Institute of Standards and Technology (NIST), under the oversight of its Time and Frequency Division, which is part of NIST's Physical Measurement Laboratory based in Gaithersburg, Maryland.
WWV Transmitter Building (2002 or earlier)
Alongside weekly broadcasts over WWV, in May 1920 the Bureau of Standards presented the "portaphone", with which one could "receive wireless impulses in the form of signals, music or speech, reproducing the same through a loud-speaking telephone and horn".
WWV seconds pulse generator, 1943
A 1940 QSL card for WWV
Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz ; above the medium frequency band (MF), to the bottom of the VHF band.
Grundig Satellit 400 solid-state, digital shortwave receiver, c. 1986
Radio amateurs carried out the first shortwave transmissions over a long distance before those of Guglielmo Marconi.
National Panasonic R3000 analog shortwave radio receiver, c. 1965.
Portable shortwave receiver's digital display tuned to the 75–meter band