What changed
From spark to software — edited Sep 5, 2026 by Unknown editor
Compared with the version from Aug 31, 2026. Note: Imported from content/wiki
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two-way crossing in November 1923 were done by amateurs pushed onto "worthless" short wavelengths a
decade earlier.
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Calibration arrived with them: **WWV** began broadcasting time and frequency standards in **1923**,
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and for decades an amateur checked a crystal or a dial against it. By **1926** Brandon Wentworth,
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6OI, had confirmed contact with every continent — the first Worked All Continents, three years after
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the first two-way crossing of the Atlantic. See [DX and awards](/wiki/operating/dx-and-awards).
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## AM to single sideband, 1930s–1960s
Amplitude modulation dominated HF voice for decades. **Single sideband** — experimented with by
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practical with a few watts, and digital signal processing brought noise reduction and sharp filtering
into ordinary radios.
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The decade also closed the commercial chapter of the mode amateurs kept: the last North American
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coast stations working Morse shut their keys down in **July 1999**. Ship-to-shore Morse ended;
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amateur CW did not.
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## Software-defined radio, 2000s onward
Moving the demodulation into software collapsed the cost of a good receiver and gave every operator a
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Every one of these transitions was resisted, and every one of them was carried out by amateurs
experimenting on their own equipment. The next one is probably already running on somebody's bench.
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## Sources and further reading
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- [AC6V's amateur radio history](https://ac6v.com/history.php) — Rod Dinkins, AC6V (SK): a
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year-by-year chronology, and the source for the WWV, Worked All Continents and 1999 coast-station
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dates here.
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- [NIST time and frequency division](https://www.nist.gov/pml/time-and-frequency-division) — WWV
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and WWVH today.
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Back to [amateur radio history](/wiki/radio-history), or read about
[the people behind it](/wiki/people).