1923: The Shortwave DX Breakthrough in Amateur Radio

Part of our The Evolution of Amateur Radio timeline series.

Remember that the government handed amateurs the shortwave spectrum above 1.5 MHz back in 1912 because they figured it was useless for anything but local contacts. In 1923, hams proved everyone wrong, and in the process turned amateur radio from a local curiosity into a global hobby.

The transatlantic tests

The groundwork was actually laid in late 1921, when Paul Godley, 2ZE, traveled to Scotland with American amateur equipment and successfully received signals from station 1BCG in Greenwich, Connecticut, on the short wavelength of 230 meters. That was the first confirmed transatlantic amateur contact, and it caught fire from there. By 1923, two-way transatlantic contacts between American and European amateurs on shortwave had become achievable and repeatable, not just a one-off stunt. The first confirmed two-way transatlantic amateur QSO happened that November, between Leon Deloy, 8AB, in Nice, France, and American stations 1MO and 2XK, a moment that proved shortwave wasn’t just good for receiving distant signals but for genuine back-and-forth conversation.

Why nobody expected this to work

The physics behind the breakthrough wasn’t fully understood by the amateurs who stumbled into it. What they’d found, without the vocabulary to explain it yet, was that shortwave signals could refract off the ionosphere and skip back down to earth hundreds or thousands of miles away, a mechanism scientists wouldn’t formally characterize for several more years. Commercial and government wireless engineers of the era had built their entire long-distance strategy around longwave transmission, using enormous, expensive antenna arrays and massive amounts of power precisely because they believed shorter wavelengths were only good for short hops. Amateurs, tinkering on shoestring budgets with whatever wavelength the government had let them keep, ended up discovering by accident what turned out to be a far more efficient way to cross oceans.

The receiver technology catching up: the superheterodyne

The DX breakthroughs of this era weren’t just about antennas and luck. They coincided with a fundamental leap in receiver design. Edwin Armstrong, working for the US Army Signal Corps in Paris, conceived the superheterodyne circuit in February 1918 while trying to solve the problem of picking weak enemy shortwave signals out of a noisy environment, and filed his US patent that December. The technique converts an incoming radio signal to a fixed intermediate frequency before amplifying and filtering it, which gives a receiver far more sensitivity and selectivity than the tuned radio frequency and regenerative designs hams had relied on up to that point. RCA began marketing superheterodyne receivers commercially in March 1924, and the architecture quickly became the standard for both broadcast and amateur receivers through the rest of the 1920s and into the 1930s. It’s not an exaggeration to say the superheterodyne principle Armstrong worked out in 1918 is still, in modified form, the architecture underneath most amateur receivers built before the SDR era.

The amateur census hits 14,000

The excitement translated directly into growth. The 1923 amateur census put the number of licensed US hams at roughly 14,000, more than double the prewar peak, as word spread that these supposedly worthless frequencies could put an amateur station in contact with the other side of the planet using a fraction of the power commercial stations needed on longwave.

New privileges and a new top license class

Regulators responded by creating the Amateur Extra First Grade license in 1923, a new top-tier class that conveyed extra operating privileges beyond the existing First and Second Grade licenses, on top of a tougher written exam and a 20 word per minute code test. It’s a direct ancestor of the Amateur Extra class that still exists today as the top license tier in the US. New bands followed close behind: in 1924, amateurs were allocated dedicated segments at 80, 40, 20, and 5 meters, with spark-gap transmitters banned outright on the new allocations in favor of cleaner continuous-wave signals.

An international movement forms

The transatlantic breakthroughs made it obvious that amateur radio was no longer a national hobby. On April 17, 1925, delegates from 23 national amateur societies met in Paris and formed the International Amateur Radio Union to coordinate frequency allocations and represent amateur interests at international conferences, with ARRL founder Hiram Percy Maxim serving as its first president. That coordinating role is still central to the IARU today whenever the ITU takes up spectrum decisions that affect the amateur bands. QSL cards, the postcards hams exchanged to confirm a contact, took on new importance in this era too, since confirming a transatlantic contact on paper was often the only proof an operator had that the far-fetched claim was real.

Shortwave goes to the ends of the earth

The practical implications showed up fast. Donald MacMillan’s 1923 Arctic expedition carried an amateur station operating on 200 meters as its primary means of communication, the first expedition to do so. Over the following decade, dozens of Arctic and Antarctic expeditions, including Admiral Byrd’s, relied on amateur radio operators back home to relay messages, because commercial and government wireless simply couldn’t reach that far with the equipment available.

Why 1923 still matters

Every HF DX contact you make today, whether it’s a quick FT8 exchange or a rag chew on 20 meters, traces back to this single year when amateurs proved the shortwave spectrum wasn’t a consolation prize. It was the best real estate in radio, and it’s the reason HF DXing is still the heart of the hobby a century later.

Sources

Previous: 1912, the Radio Act. Next up: 1934, when the FCC took over.

1923: The HF DX Breakthrough That Changed Everything