LONDONDERRY-CHELTENHAM DATA MODEM TRIALS OF 1968 - (TEST PLAN, INSTRUMENTATION, AND LOGISTIC ASPECTS).

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 bitssecond. The FSK modem was the duobinary, 16 channel ANFYC-9. The three DPSK modems that were tested were the 16 channel ANUSC-10V, the 12 channel MD-671SRC, and the Model 35. The Model 35 was a digital implementation of the ANUSC-10V. 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. Author