SAFOC HF Digital Data Link (Phase II - System Tests).
Research and development technical rept.,
ARMY ELECTRONICS COMMAND FORT MONMOUTH NJ
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The basic Semiautomatic Flight Operations Center, the airborne subsystem, the communications equipment, the test aircraft, and the Granger antenna were integrated into a total system configured to permit performance testing using the HF digital data link. The message exchange consisted of a burst type of 33-bit up-link interrogation and a 77-bit down-link response. Preliminary tests using an old analog HF modem realized an average 78 percent error-free message exchange rate. The integration of a new all digital HF modem increased this average to 88 percent. Tests were conducted both line-of-sight and much more beyond line-of-sight. The maximum beyond line-of-sight range flight distance was 129 miles. Analysis of the reduced data indicates that with a single bit error-correcting technique, an error-free message exchange rate of 94 percent is expected. Other recognized improvements within the state-of-the-art are the replacement of the ANARC-102 transceiver by the ANARC-98 transceiver with built-in design features more suited to digital data transmission, and the replacement of the present HF helicopter wire antenna with a newly developed and more efficient Nearly Vertical Incidence Skywave NVIS HF antenna. In addition to planned changes in system timing, the new transceiver will allow changes to reduce polling time. Author
- Voice Communications