PHASE B TECHNICAL REPORT MULTIPLEXER SET AN/FCC-17( ) AND MULTIPLEXER SET AN/MCC-12

摘要

Phase B equipment fabricated by Lenkurt Electric Co., Inc., San Carlos, California, included 72 two-way channels of the 600-channel fixed office Multiplexer Set AN/FCC-IT and 60 two-way channels of the 60-chan-nel tactical Multiplexer Set AN/MCC-12 as well as all common equipment such as carrier supplies, group and supergroup transmission equipment, power supplies, and alarm equipment. The fixed office equipment (600 channels) occupies ten 7-foot 6-inch racks, and the tactical equipment mounts on three 7-foot racks in a mobile shelter. Category I tests were performed on- the complete systems to determine compliance with electri¬cal requirements and oh representative equipment samples to determine compliance with mechanical requirements. The mechanical and electrical design is completely in accordance with military specifications, result¬ing in a multiplexer set that is reliable and physically rugged. The multiplexer set has also been designed for ease of maintenance by semi¬skilled personnel, featuring interchangeable plug-in units and built-in test facilities.nThe Category I tests demonstrated the excellent electrical charac-teristics of the multiplexer set. The twin channel modulation scheme results in low channel envelope delay distortion and flat frequency re-sponse over the maximum possible bandwidth of the U-kc channel increment. These two factors plus the full loading capability of the channels meet the needs of data transmission. Statistically, the envelope delay re-quirements are met, and overall, the channel characteristics are extreme-ly good :the adjacent channel crosstalk is excellent, less than 20 dbaO;the channel frequency response is relatively flat and very wide, average 3 db points are at 225 and 36OO cps and response is within 1.5 uu between 325 and 3450 cps;and the channel envelope delay is less than 1 millisecond between 600 and 3200 cps over six tandem links and less than 130 microseconds between 1000 and 2500 cps over one link.nElectrical system performance tests initially revealed noise pro¬blems, but these problems were resolved and the resulting system noise performance snowed that the idle noise and loaded noise were very low. The idle noise is less than 15 dbaO, and the loaded noise is less than 23 dbaO for 100 percent data loading at -5 dbmO. The channel harmonic distortion is less than -4O dbmO. The load handling capability of the multiplexer set is greater than the 100 percent data load of -5 dbmO per channel required by the specification, assuring system performance up to any expected usage despite probable adverse conditions of operation.nTemperature tests on the multiplexer set show little effect on the channel frequency response and the envelope deli, distortion over the range 0°C to +52°C. The ferrite pot core characteristics are not pre¬dictable at temperatures below -20°Cj therefore, the channel response characteristics could not be perfectly compensated, and the results show a more significant change of envelope delay a^:frequency response at -29°C As a result of Category I tests, the mechanical design of major as¬semblies was modified to eliminate susceptibility to vibration and shock damage. Also, the steering mechanism on the tactical system trailer van was modified to improve steering control and strengthen the tow bar. These van modifications reduced the possibility of fracture during turn-ing.nThe multiplexer set has been designed and fabricated for reliability under extreme conditions of operation. Reliability testing under actual field conditions and with military maintenance indicates an MTBF in ex¬cess of 411 hours, although the calculated MTBF for a 60-channel system is 125 hours. Further field experience has shown the actual MTBF to be better than 800 hours and the availability of any channel to be 99*98 percent. The availability of a particular channel is 99-998 percent.