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1st 50th Infantry Association

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1. GS Radar in Vietnam
2. Radar Section Personnel
3. Radar Section Organization
4. AN/PPS-4 Radar Set
5. AN/PPS-5 Radar Set

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Ground Surveillance Radar Section
1st Battalion (Mech) 50th Infantry

Mike Hartz, Radar Operator

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Ground Surveillance Radar (GSR) in Vietnam

Ground surveillance radars where frequently used in NDP's, Laagers and Fire Support Bases. In these positions they were employed to cover the most likely avenues of approach and could thus give the Commanding Officer some forewarning of an impending attack.

The AN/PPS-4 (shown above) and AN/PPS-5 radar sets (photo at right) were short range ground surveillance radars that made use of the doppler effect to detect a target. The sets detected the difference in frequency between the echoes reflected from stationary objects and the echoes reflected from moving objects, and presented this information as a target indication to the radar operator. To detect a moving target the radar set needed to receive echoes from a fixed object together with the echo from a moving target.

The echoes from fixed objects were called ground clutter. The radar sets presented audio indications of targets from only a relatively small segment of the radar beam at any given time. This segment of range is called a range gate. Target echoes were constantly being received by the radar receiver throughout the length of the beam however, only target echoes from the range gate segment of the radar beam were indicated audibly to an operator.

Right: AN/PPS-5 Radar Set

The radar sets were used primarily to provide short- and medium-range identification and location of enemy targets during periods of limited visibility. The AN/PPS-5 radar had a maximum range of 5 kilometers and the AN/PPS-4 radar had a 1.5-kilometer range for personnel detection. Both were used to protect the night defensive positions. The PPS-5 is a larger and less portable unit, with the motorized disk typically set up on top of a tower amd cables running down to the bunker where the control unit was located. It was typically run off a generator whereas the PPS-4 used batteries.

1/50(M) Battalion Ground Surveillance Radar Section Personnel

Section Leaders

                    Radar Operators

James Amrein
Kenneth Becker
Gene Bucholz
Alan Carpenter
Rex Crisswell
Mike Hartz
Allen Hendricks
James Holloway

Battalion Ground Surveillance Radar Section Organization



M113A1 Armored Personnel Carrier,
1 x E-6 (Section Leader), Pistol
1 x E-5 (Senior Radar Operator), Pistol
1 x E-4 (Driver, Radar Operator), Pistol, M-79
1 x AN/PPS-4
1 x AN/GRC-125

M113A1 Armored Personnel Carrier
1 x E-5 (Senior Radar Operator), Pistol
1 x E-4 (Driver, Radar Operator), Pistol, M-79
1 x AN/PPS-4
1 x AN/GRC-125
Radar Maintenance MOS 96R, Operator MOS 26C

AN/PPS-4 Ground Surveillance Radar

The AN/PPS-4 is a small self contained unit. It sits on a tripod, in total about four feet high, and could be carried by a single person. The dish and controls were all part of a single unit which we would set up on its tripod right on the ground. We plugged the earphone into it and panned the unit back and forth manually. Output was through the earphones and dials on the unit showing distance to the target.

AN/PPS-5 Ground Surveillance Radar

REFERENCE: TM 11-5840-298-12

The AN/PPS-5B Ground Surveillance Radar Set is a lightweight, man-portable, battery-powered, ground-to-ground surveillance radar set for use by units such as infantry and tank battalions. The radar is used to detect, locate, identify and track moving personnel at ranges of 6km and vehicles at ranges of 10km, day or night under virtually all weather conditions.

The radar has a maximum display range of 10,000 meters and targets can be displayed both aurally and visually. Built for durability, the AN/PPS-5B Radar is rugged enough to withstand rough field handling. When packed in its watertight container, it can be parachute dropped and undergo repeated submersion. Increased operational flexibility is afforded when the unit is mounted in a jeep or APC.

When emplaced, the radar set consists of two major operating assemblies (tripod mounted components and control indicator (CI)). The two major assemblies are connected by a remote cable. The tripod mounted components include the radar receiver-transmitter, antenna reflector, battery assembly, and telescope. The CI receives output from receiving circuits of the transmitter and presents them on the A and B scopes and as audible signals in the electrical headsets. The radar control indicator controls the movement of the antenna in azimuth. The power for the CI is received through the remote cable from the battery assembly on the radar receiver-transmitter or through the power supply. Communications are provided by secure combat net radio (CNR).

The system includes everything necessary for operation including 24 VDE external power converter, carrying harnesses, tripod, an adapter for vehicle mounting, four (4) rechargeable batteries (BB-622) and a fifty (50) foot cable for remote operations.

The AN/PPS-5 unit has a square screen similar to the round radar screens in the movies with blips and so forth. A line representing the radar beam moves across the screen side to side.

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