ANTENNA MISALIGNMENT TROPOSCATTER TEST PROGRAM.

Troposcatter Communications experiments were conducted to determine the degradation in performance which results when the antenna system becomes misaligned and also to determine the improvement in performance which results when employing angle-diversity techniques. The antenna misalignment tests were performed on 105 and 170 mile paths using 8 GHz radio equipments. The 105 mile path employed dual-space-diversity eight-foot antennas. The 170 mile path employed twenty-eight foot angle-diversity antennas. Misalignment on the 105 mile path was achieved by a physical misalignment of the eight-foot antennas on both azimuth and elevation. Misalignment on the 170 mile path was simulated by operating thru any one of ten off-set feedhornbeam. Performance as a function of misalignment was determined in terms of received signal level, fade rate, and the BER bit error rate of a binary FSKTDM modem operating at rates from 154 kbs up to 1.228 mbs. The angle diversity experiments were conducted on the 170 mile path using the 8 GHz radio equipment and the angle-diversity antennas mentioned above. Performance as a function of 1, 3, 5, 7 orders of angle diversity was determined for both binary FSKTDM and FMFDM operation. The FSKTDM performance was that of BER for 154 kbs to 1.228 mbs transmissions for FMFDM it was the BER of a 2400 bs and a 40.8 kbs modem operated thru a voicegroup channel of a 24 voice channel system. Author