Dgital HF Communication System for Long-Distance Air-to-Ground Communication
Klaus W. Otten · IEEE Transactions on Aerospace and Navigational Electronics · 1964
Design characteristics and test results of an HF digital communication system for long-distance (several thousand miles) air-to-ground communication are described. The system was designed to operate reliably under adverse (multiple) propagation conditions by applying frequency and time diversity in form of quantized frequency modulation (QFM). Comparative tests with an audio-frequency-shift keying (AFSK) system under equal conditions show significantly better performance for the QFM system.