W1HRX 1936 Malden, MA

The callsign W1HRX is that of James Millen, of the famous National Company (HRO et al). The US amateur "5 meter band" of 56-60 MHz was allocated from October 1927 and only withdrawn when the US entered WW11 in December 1941.The National SRR ("super regenerative") receiver was produced between 1933 and 1935, superceded by the National 1-10 (not a superhet, but a new design super regen with RF stage). The RCA 800 is a transmitting triode introduced by RCA in October 1933; the RK 18 (a Raytheon tube) of similar vintage.

"Beam array directed towards Hartford" undoubtedly refers to the ARRL laboratory at Seldon Hill, Hartford, CT. established in 1931, "In 1932, regular testing of UHF [meaning 56 MHz and above] receivers, transmitters and antennas was in full swing." - Amateur Radio magazine, Issue 1 - 2022. ". . the early days of UHF exploration continued at Selden Hill throughout the mid-1930s."

QSL from the estate of W9RBO / K3AMO
Info courtesy of VK2ZRH, VK3BDL