RADAR FREQUENCIES

                                                       RADAR FREQUENCIES                                                                                Conventional radars generally have been operated at frequencies extending from about 220 MHz to 35 GHz, a spread of more than seven octaves.These are not necessarily the limits, since radars can be, and have been, operated at frequencies outside either end of this range. Sky wave HF  over-the-horizon (O T H) radar might be at frequencies as low as 4 or 5 MHz,and ground wave HF radars as low as 2 MHz. At the other end of even higher frequencies. The place of radar frequencies in the electromagnetic spectrum is shown in Fig. 1.4 some of the nomenclature employed to disignate the various frequency regions is also shown.Early in the development of radar, a letter code such as S, X,L,etc,,,,,, was employed to designate radar frequency bands.Although its original purpose was to guard military secrecy, the designations were maintained, probably out of habit as well as the need for some convenient short nomenclature.This usage has continued and is now an accepted practice of radar engineers. Table  1.1 lists the radar-frequency letter-band nomenclature adopted  by the IEEE.15 These related to the specific bands assigned by the internationals Telecommunications Union for radar. For example, although the nominal frequency range for L band is 1000 to 2000 MHz ,an L-band radar is thought of as being confined within the region from 1215 to 1400 MHz since that is  the extent of the assigned band.