AN/MPQ-4
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 AN/MPQ-4 | |
| Country of origin | US |
|---|---|
| Manufacturer | General Electric |
| Introduced | 1958 |
| Type | Counterbattery |
| Frequency | 16 GHz (Ku band) |
| PRF | 7000 pps |
| Beamwidth | 14.25 mils (0.362 mm) |
| Pulsewidth | 0.25 μs |
| Range | 225 to 15,000 m (738–49,213 ft) |
| Azimuth | 25°, but rotatable through 180° |
| Elevation | −6° to +12° |
| Precision | 50 m at 10,000 m |
| Power | 50 kW |
| Other names | JAN/MPQ-N1 Type 72 |
The Radar Set AN/MPQ-4 was a US Army counter-battery radar primarily used to find the location of enemy mortars and larger artillery in a secondary role. Built by General Electric, it first entered service in 1958, replacing the earlier and much simpler AN/MPQ-10. The MPQ-4 could determine the location of an enemy mortar in as little as 20 seconds by observing a single round, whereas the MPQ-10 required several rounds to be launched and could take 4 to 5 minutes to take a "fix". The MPQ-4 remained one of the primary US counter-battery systems through the late 1970s until it was replaced by passive electronically scanned array radars like the AN/TPQ-36.
In accordance with the Joint Electronics Type Designation System (JETDS), the "AN/MPQ-4" designation represents the 4th design of an Army-Navy electronic device for ground mobile radar combination equipment. The JETDS system also now is used to name all Department of Defense electronic systems.
During World War II, operators of the newly introduced SCR-584 radar noticed they could sometimes see artillery shells in flight. With considerable effort, they could follow these rounds and then manually estimate the radial trajectory. By looking along that path, they could see the rounds being launched and then forward that information to friendly artillery units.[1]
The US Army's first counter-battery radar was the AN/MPQ-10. This was essentially a smaller version of the SCR-584 mounted on a Bofors 40 mm gun carriage. Introduced in 1951, the system remained manually operated, although with a few modifications to make the operation somewhat similar. Tracking down an enemy mortar generally took on the order of 4 to 5 minutes, and required a number of rounds to be fired.[2] The AN/KPQ-1 attempted to improve on this by using five radar antennas aimed at slightly different angles horizontally, spreading the beam out so it covered a larger area of the horizon.[3]
A better solution to the problem of seeing the first round had been developed by John Stuart Foster while working at the MIT Radiation Laboratory as part of a technical exchange from the Canadian National Research Council. The Foster scanner was a mechanical system that rapidly scanned moved a radar signal back and forth along a selected axis. For the counter-battery role, the beam was scanned horizontally, so any round launched across a wide angle in front of the radar would be seen as it passed through the fan-shaped beam.[4]
The AN/MPQ-4 was the first operational counter-battery radar to use the Foster scanner. It entered service in 1958, sending the MPQ-10 to secondary roles, mostly for tracking outgoing rounds from friendly artillery for adjusting fire.[5] The MPQ-4 was widely used in the Vietnam War, where it was often emplaced on short wooden platforms to provide an improved view of the horizon.[6][7]
Digital electronics and passive scanning of the signal made the MPQ-4 obsolete. Two replacements were developed, the AN/TPQ-36 and the larger AN/TPQ-37 Firefinder systems, with the TPQ-36 undergoing extensive qualification testing between 1975 and 1979 and entering deployed service in 1982.[8]
