FWIW- here is a description of a trial involving the FCY-9 modem & two others:
"LONDONDERRY-CHELTENHAM DATA MODEM TRIALS OF 1968 - (TEST PLAN, INSTRUMENTATION, AND LOGISTIC ASPECTS).
Descriptive Note : Interim rept.,
Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C
Personal Author(s) : Kahler,F. C. ; McGown,M. Y. ; Jewett,W. M.
Report Date : DEC 1968
Pagination or Media Count : 31
Abstract : An evaluation was made to compare the performance of a frequency-shift-keyed (FSK) type modem with differentially coherent phase-shift-keyed (DPSK) type modems operating over an HF radio path. Tests were conducted during the period 10 June 1968 to 3 August 1968 with transmission from the U.S. Naval Communication Station, Londonderry, Northern Ireland to the U.S. Naval Communication Station, Cheltenham, Maryland. The RF communication system was of the single sideband type. The data rate was 2400 bits/second. The FSK modem was the duobinary, 16 channel AN/FYC-9. The three DPSK modems that were tested were the 16 channel AN/USC-10(V), the 12 channel MD-671(SRC), and the Model 35. The Model 35 was a digital implementation of the AN/USC-10(V). Bit error rate data were collected on each modem over one minute periods. Each one minute period was associated with a three minute period during which the propagation path was characterized. Analysis of this data has not been completed. The report covers the test plan and instrumentation that was used."
Nothing on shipboard gear.
--- In email@example.com, Nick England <navy.radio@...> wrote:
> I've got some interesting AUTOSEVOCOM info in section 3.11 at
> I *think* STEAMVALVE was the HF link consisting of an AN/FYC-9 modem
> at shore sites plus shipboard modem + KG-13 crypto + HY-2 vocoder
> Is this right? Anyone got more info about what was used shipboard?