Serial data transmission over HF radio links

The paper reports on an investigation into the use of HF radio links for serial data transmission. A prototype test system was developed and used to study the effectiveness of varios methods of modulation and demodulation, to study ways of varying the data rate, to exmine the performance of serial systems as a function of data rate and to investigate the use of adaptive equalisation as a technique for overcoming multipath interference. Data was transmitted at rates ranging from 0.3 kbit/s to 3.6 kbit/s, and the associated error probabilities were found to be in the range 1.5 ¿¿ 10¿¿2 to 5.8 ¿¿ 10¿¿2. The use of equalisation resulted in improved system performance over the entire range of data rates.