Converging on the Half-Metre Wave: Parallel Point-to-Point Radio Programmes in Italy and Japan, 1929–1933

Between 1929 and 1933 two national research programmes pushed point-to-point radio toward the half-metre wave (the decimetric band around 600 MHz) largely independently of one another: one led in Italy by Guglielmo Marconi, the other in Japan by Shintarō Uda at Tōhoku Imperial University. Drawing on both leaders’ own published accounts, this paper reconstructs the two efforts side by side and argues that they converged on frequency while diverging on antenna paradigm (i.e. parasitic end-fire array versus cylindrical parabolic reflector) and, decisively, on outcome. Italy placed the half-metre wave into permanent service with the Vatican–Castel Gandolfo radiotelephone at 600 MHz (1932) and drove a 270 km over-horizon link across the Tyrrhenian Sea to Cape Figari in Sardinia; Japanheld the era’s UHF distance record with the 600 MHz Sendai–Ōtakamori link (1929), yet fielded its operational island circuits at VHF. The study closes on a documented 1933 assignment of Yagi’s British patents to the Marconi company, a factual coda distinct in evidentiary status from a differently grounded account examined in a companion study