DATA TRANSMISSION INVESTIGATION (SHORT RANGE HF RADIO DATA TRANSMISSION).

The short range HF radio link was analyzed for its capability in transmitting digital data. The report presents and discusses results obtained in field tests conducted over the radio link of lengths 25, 47, 65, 94, and 220 miles. The equipment used for conducting the tests are also described in detail. The tests include general observations of link conditions, data transmission test with and without inband diversity, phase measurement test to define the coherency of the short range HF path, fade measurement test of several CW tones to define the depth, length, rate and degree of frequency selective fading, multipath test to aid in determining the severity of multipath. Two radio sets were used to conduct the field test. The major radio set was a commercial SSB radio set with the AGC defeated to permit the measurement of the HF path for its fading characteristics. The second radio set was the ANGRC-106 which was briefly used to test its capability of transmitting digital data. The results of the aforementioned tests are presented in tabular and graphical form. Diurnal variations, channel conditions, expected data transmission performance, and the optimum signaling element length for data transmission over the HF path is discussed. Author