Just to add a bit to the R-1051 story, the "B" model was also used by the Royal Canadian Navy. As well as HF, it was also used for low frequency coverage with the addition of a CV-5086/URR converter.  This converter was manufactured by Elmer (Italy) or Instronics (Ontario) and used with the AN/SRA-17 LF antenna. I have two of the AN/SRA-17 systems but never saw any of the RCN R-1051's or their LF converters in surplus channels and would be interested to hear if anyone ever came across them.