The RAT and RAT-1 receivers covered 13.5 -20 and 20-27 mc, as did the RAV series. These were built in 1939 and 1950 and there were no more than 100 or so of all designations. There were no transmitters in these frequencies. The rarest of all are the 9-13.5 mc receivers of which no examples have survived in good condition. - Gordon White