Type 965 radar

The Type 965 radar was VHF (P band) long-range aircraft warning radar used by warships of the Royal Navy from the 1960s onwards. The Type 965M, Type 965P, Type 965Q and Type 965R were improved versions; the Type 960, 965M and 965Q used the single bedstead AKE(1) aerial, whilst the Type 965P and 965R used the double bedstead AKE(2) aerial.

The 965 is ultimately designed to a May 1950 requirement for a further updated version of the 1945 Type 960. The 960 provided long-range early warning on small ships, but had a very wide beam at 35° horizontal. In 1954 the idea of a general-purpose frigate with the ability to provide some fighter direction arose, which required a radar with a much narrower beam. Marconi responded with the 965, reducing the beam to 12°. Based on WWII technology, the 965 was subject to considerable radar clutter from waves. The Type 965Q and 965R were improvements on the 965M and 965P respectively, adding a COHO-based moving target indication (MTI) mode to suppress clutter. Designed before the introduction of Doppler filtering, it was not able to detect low-level targets against a background, either landforms or high waves.

The lack of a true MTI proved to be a serious problem during the 1982 Falklands War, which ultimately led to the loss of HMS Coventry (D118) where Argentine aircraft could not be seen against the background of the islands. Similarly, the Type 965 could not detect aircraft flying low; the two Argentine Navy Super Étendards that caused the loss of HMS Sheffield (D80) were not detected by Type 965R radar when they were flying at 30 m, but were shown as contacts by HMS Glasgow (D88)'s Type 965R radar when they popped up to 120 ft above sea-level at 45 nmi, though it was the UAA1 radar warning receiver that drew attention to the contacts.

The Type 965 radars used radio frequencies that were used by television stations, and therefore caused interference with television (and vice versa) if used near land in Europe. Type 965 was superseded by the Type 1022 radar, which did not have this disadvantage.

Adoption
During 1954-55, reports on most fleet exercises showed that there was an urgent need for radar picket ships. These would require a suitable radar. The need for such a radar had been raised as a staff requirement in May 1950. In 1955, four radars were considered:
 * The American AN/SPS-6C radar, which was credited with a range of 50 nmi at 15,000 ft, and 90 nmi at 60,000 ft.
 * The Dutch LW-02 radar, which was credited with a range of 75 nmi at 35,000 ft.
 * A Marconi's Wireless Telegraph Company commercial design originally conceived for land-based air defence, which was credited with a range of 70 nmi at 35,000 ft.
 * Extending the range of the Type 992 radar, by slowing its scanning rate.

A potential route for the Royal Navy to get the SPS-6C was the Mutual Defense Assistance program (MDAP), but by 1954-5 the programme was running down. In addition, it was thought that getting spares for the SPS-6C radar could be a problem, because the United States Navy considered it obsolescent. The Marconi design was chosen and was named Type 965. The Type 965M was introduced in about 1960, and used the original AKE(1) aerial with an improved receiver and feeder.

Ships with Type 965 radars

 * Type 965M with AKE(1) aerial
 * The aircraft carrier HMS Ark Royal was given a Type 965M system on her foremast when modernised in 1958-59.
 * Type 41 Leopard-class frigates when modernised.
 * Type 81 Tribal-class frigates.
 * Type 12M Leander-class frigates (though removed in the eight ships given the Ikara conversion in 1970-78 and the five ships given the Seawolf missile conversion in 1978-84).
 * Weapon-class destroyers modernised to air direction destroyers.
 * County-class destroyers Batch 1.
 * The aircraft carrier HMS Centaur when refitted in 1963. The radar was taken from the air direction destroyer Battleaxe.
 * Tiger-class cruisers when modernised in the late 1960s.
 * The carrier HMS Hermes when converted from the aircraft carrier role to the commando carrier role in 1971-73.
 * Type 965P with AKE(2) aerial
 * Battle-class destroyers - the four that were modernised to air direction destroyers.
 * Type 61 Salisbury-class frigates when modernised in 1961-68. HMS Chichester had her Type 965 removed in 1973 when she was refitted as Hong Kong guardship.
 * County-class destroyer Batch 2.
 * The aircraft carrier HMS Eagle was given a Type 965Q on her lattice foremast when modernised in 1959-64.
 * Type 82 destroyer, the sole ship HMS Bristol described as "Type 965 with double AKE array and IFF".  before it was replaced by Type 1022 radar when she was modernised in 1984-6.
 * Type 965Q with AKE(1) aerial
 * Type 965R with AKE(2) aerial
 * The aircraft carrier HMS Ark Royal was given two Type 965R systems on separate masts when modernised in 1967-70.
 * Type 42 destroyer Batch 1; Batch 2 had the Type 1022.

Technical specifications
A common aerial was used for transmitting and receiving. This was the single bedstead AKE(1) in the Type 965M, and the double bedstead AKE(2) in the Type 965P. The 965M and 965P were integrated with IFF Mk 10. The radar displayed both to an "office display unit" (monitor unit design 44), and up to six remote plan position indicator (PPI) displays.


 * Differences between Type 960 and 965M
 * Type 965 receiver noise factor: 8 dB.
 * Type 965M receiver noise factor: 4.5 dB.
 * Type 965M feeder was 1 dB better than the Type 960 feeder.


 * Range
 * Type 960: credited during appraisal as 70 nmi at 35,000 ft.
 * Type 960: 120 nmi against an English Electric Canberra at 20,000 ft.
 * Type 965M: 200 nmi at 45,000 ft.
 * Type 965P: 280 nmi at 100,000 ft.

Type 965Q and 965R
The receiver of the Type 965Q and 965R used "a coherent oscillator (COHO) to provide the coherence in phase between transmission and reception. The COHO is phase locked to the transmitter pulse." With the Type 965Q and 965R, the pulse repetition frequency (PRF) had a number of different settings.
 * In non-MTI mode, the PRF was set by the Pulse Synchronising Outfit RSE.
 * In MTI mode, to avoid interference from other radars, there were five available pulse intervals, each with a corresponding stagger time. Pulse intervals were ±3 μs; stagger times were ±2 μs.
 * 2580 μs pulse interval ±516 μs stagger time
 * 2590 μs pulse interval ±518 μs stagger time
 * 2600 μs pulse interval ±520 μs stagger time
 * 2610 μs pulse interval ±522 μs stagger time
 * 2620 μs pulse interval ±524 μs stagger time