[Milsurplus] SRR-13 question

[Ray Fantini]

Wonder if the AN/FRR-21 and SRR-11 drifted as bad as the HF version the SRR-13, and what was the point of the SRR-13? Was it supposed to replace the R-390 for shipboard operation? Or was it used between the old WW2 series RA/RB and the like stuff and later replaced by the R-390 and being that the R-390 was built as a ground base Army radio was the navy so annoyed at this that went to something like the SRR family of radios? And last but not least what was the line of radios deployed for HF operation? Was it SRR to R-390 to R-1051? Or R-390 to SRR to 1051?
Ray Fantini KA3EKH