- Early versions of what would become AA No. 3 Mk. 7. Also known as "GLAXO". AA No. 3 Mark 5 - UK name for US-built SCR-584 used from 1944 onwards. AA No. 3 Mark 6 - Post-war Canadian lock-follow design, not taken into service. AA No. 3 Mark 7 - Post-war version of AA No. 3 Mk. 4, standard AA radar into the 1960s. AA No. 3 Mark 8 - UK name for US-built SCR-545, not taken into service. Number 4 AA Number 4 was a wide collection of short and medium-range systems known as tactical control radars, whose main purpose was to provide cueing support to the AA Number 3 radars, or "putting on". There were seven entries: AA No. 4 Mark 1 - Canadian design rapidly developed from Air-Sea Vessel radar electronics. Widely used with GL Mk. III systems and later. Known in Canada as the Zone Position Indicator, or ZPI. AA No. 4 Mark 2 - UK-built versions of the Mark 1. AA No. 4 Mark 3 - Similar to Mark 1 and 2, but operating on Airborne Interception radar frequencies. Two sub-versions, (V) which was Vehicle mounted (on a truck) and (P) which was Portable. AA No. 4 Mark 4 - UHF set working at 600 MHz, not taken into service. AA No. 4 Mark 5 - Expedient development working in the S band, only small numbers used. Also known as "Gorgonzola" due to the shape of its antenna. AA No. 4 Mark 6 - Canadian S band development, highly portable. Known in Canada as the Microwave Zone Position Indicator, or MZPI. AA No. 4 Mark 7 - UK system similar to the Mark 6 but using a cheese antenna. Some sources state an early name for the Orange Yeoman was Mark 7, but it is more likely that would have been Mk. 8 or part of Number 5 series. Number 5 AA Number 5 was assigned to radars similar to Number 4 in concept, but with longer range. These were to be assigned to the Anti-Aircraft Operations Rooms (AAORs) to provide early warning and tactical control over a metropolitan-sized area. There were two entries: AA No. 5 Mark 1 - 209 MHz (VHF) AA No. 5 Mark 2 - 600 MHz (UHF) Number 6 AA Number 6 was a special-purpose system dedicated to rangefinding for light anti-aircraft guns, namely the Bofors gun. Short-range AA