FMCW swept-frequency sounding has been used within centralized spectrum management networks to provide real-time channel evaluation (RTCE) for multiple HF circuits. Often referred to as “chirp” sounders, these devices provide the benefits associated with oblique incidence sounding, i.e. for use in the optimization of frequency utilization, improvement in circuit reliability, evaluation of signal-to-noise and interference ratios, and the measurement of ionospheric propagation parameters used by some adaptive HF systems. When linked to centralized spectrum management networks, these sounders can be operated in limited numbers on an intermittent, low-power basis, obtaining real-time spectrum management information for multiple users. This method decreases the need for sounding in general and also limits the total time that a sounder will operate co-channel with other HF transmitters. The net result is improved information to multiple users and a decrease in interference potential due to sounding.
ITU-R F.1337 SPANISH-1997 history
1997ITU-R F.1337 SPANISH-1997 Frequency Management of Adaptive HF Radio Systems and Networks Using FMCW Oblique-Incidence Sounding