What changed
From spark to software — edited Aug 31, 2026 by Unknown editor
This is the first recorded version, so every line is shown as added. Note: Imported from content/wiki
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Amateur radio has re-invented its own equipment roughly every twenty years. Each generation looked
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like a threat to the last one and turned out to be the thing that kept the hobby alive.
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## Spark, to about 1925
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Spark-gap transmitters were simple, loud and hopelessly broad — a single station splattered across
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everything nearby. They were banned for amateur use as continuous-wave transmitters proved they could
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do more with far less spectrum. "CW" still means *continuous wave*, the technology that replaced
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spark.
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## Vacuum tubes and the short waves, 1920s–1930s
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Regenerative and later superheterodyne receivers, crystal control, and tube transmitters turned
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worldwide contacts from a stunt into routine work. The transatlantic tests of 1921–23 and the first
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two-way crossing in November 1923 were done by amateurs pushed onto "worthless" short wavelengths a
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decade earlier.
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## AM to single sideband, 1930s–1960s
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Amplitude modulation dominated HF voice for decades. **Single sideband** — experimented with by
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amateurs from the 1930s and adopted widely in the 1950s — put all the transmitter power into one
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sideband and no carrier, roughly quadrupling effective power for the same rig and halving occupied
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bandwidth. The changeover was bitterly argued at the time. SSB is still the standard HF voice mode;
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see [modulation and modes](/wiki/technical/modulation-and-modes).
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## FM, repeaters and the handheld, 1960s–1980s
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Surplus commercial FM gear on 2 meters, plus club-built repeaters on hilltops, made reliable local
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communication ordinary. The handheld transceiver made it portable. This is the era that produced the
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modern club net, the commute-time ragchew and the local emergency net — see
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[repeaters](/wiki/operating/repeaters).
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## Packet and the first digital wave, 1980s
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**AX.25 packet radio** put error-corrected digital messaging, bulletin boards and mail forwarding on
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the air before most households had an internet connection. Its descendants are everywhere:
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[APRS](/wiki/operating/digital-modes/aprs) for position and telemetry,
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[Winlink](/wiki/operating/digital-modes/winlink) for email over radio.
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## Sound cards and DSP, 1990s
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A PC sound card turned every station into a modem. **PSK31** made keyboard-to-keyboard conversation
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practical with a few watts, and digital signal processing brought noise reduction and sharp filtering
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into ordinary radios.
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## Software-defined radio, 2000s onward
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Moving the demodulation into software collapsed the cost of a good receiver and gave every operator a
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panadapter — a visual display of a whole band at once. A $30 dongle now does what a bench of
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equipment did in 1995. See [receiver performance](/wiki/technical/receiver-performance).
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## Weak-signal digital, 2017 onward
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**FT8** and its relatives decode signals well below the noise floor in fixed 15-second slots. The
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effect on operating has been enormous: worldwide contacts from a compromised antenna in an apartment,
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through a solar minimum, at 25 watts. Purists argue it is not really a conversation; the counter is
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that it keeps the bands demonstrably occupied and brings people to the hobby who then learn
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everything else. See [FT8](/wiki/operating/digital-modes/ft8).
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## What has not changed
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Every one of these transitions was resisted, and every one of them was carried out by amateurs
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experimenting on their own equipment. The next one is probably already running on somebody's bench.
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Back to [amateur radio history](/wiki/radio-history), or read about
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[the people behind it](/wiki/people).