WW2 UHF DF Outfit RU4 (what today, we would call shuff-duff - SHF DF.

  Frequency Range 2.4 to 6 Gc/s. The very first set of its kind, the confidential handbook dating from 1946. Designed to receive and D/F Pulse Modulation, Frequency Modulation and CW signals and to give a continuous indication of true and relative bearings to the transmitter. Despite the provision for these emissions it states that Pulse Modulation from radar transmitters will occupy the Outfits operational time and that it is unlikely for W/T emissions to be received at these extremely high frequencies.

  The system was for the use of 'Y' Work the forerunner of the Electronic Warfare Branch. RU4 uses receivers P63 and P64, respectively 3 to 6 Gc/s and 2.4 to 3.7 Gc/s. These are not complete receivers in the generally accepted sense since they include only the aerial input circuit, local oscillator, mixer circuit, the first two stages of IF amplification together with the requisite power supplies, whilst the other components are housed in the IF AMP M93. The following three pictures show these three units.

  This file RU4 System is a compendium of drawing and pictures of the aerial and the main parts of the system. In the file, on page 8, some of the text on the left hand side three manual controls is partially missing. From top the bottom, the controls should read:-
a. Aerial and Gyro Repeaters.
b. Manual Laying Control Magslip.
c. Rate Control Rheostat.