3rd Armored Cavalry Regiment, 1955 (Source: Ronald Greenwell) The units to the right (photo below) were Radio Teletype transmitter/receivers which we didn’t use. The units stacked directly in front in the pic were Collins 51J (shortwave) receivers (link) which were the military version of the commercial 75A series. We used both. The transmitter (behind the photographer and out of sight) was a BC-610 450 watt transmitter (link) mfgd by Hallicrafter from a commercial version of their HT-4.