April 1960 Popular Electronics
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Equipment Trailer nearest in photo, Maintenance trailer inline and connected to the rear, RAPCON separate and to the right. ASR & IFF antennas toward center of trailer, PAR Elevation antenna nearest. (circa 1979-82)
This is cool. I saw a U.S. Air Force recruitment advertisement in a 1960 edition of Popular Electronics pitching careers as radar operators (air traffic control) and technicians (maintenance). The picture has the dual-display glide path and elevation sweeps from the MPN/13/14 radar system that I worked on in the late 1970s - early 1980s. A photo I took circa 1980 of our unit based at Robins AFB, Georgia, is shown below. The precision approach radar (PAR) operated at x-band (10 GHz) with an operational range of 10 nautical miles.
B&W photo of PAR display showing Elevation display at top and Azimuth display on bottom. Yes, it is in dire need of alignment.
The azimuth and elevation antennas were mechanically swept with motors that changed the geometry of a waveguide having dipole stubs along its length. The entire PAR system was built with vacuum tubes and chassis using point-to-point wiring. Sweep patterns on the CRT were aligned using an iterative procedure to adjust linearity, x-y position, outline, size, course line and glide slope centerlines, etc. It could be quite frustrating until you got the hang of it. Unlike the airport surveillance radar (ASR) portion of the system which was used for flight path vectoring and aircraft separation while at cruising and transition altitudes, the PAR was used to guide aircraft down nearly to the ground in "blind landings." Air traffic controllers were in constant contact with the pilots giving them corrections as needed to stay centered on the line. I don't recall the decision height for USAF airplanes, but for civilian aviation in Instrument Flight Rules (IFR), it can be as low as 50 feet - that is not much time to stop a landing approach and transition to a missed approach maneuver.
Posted June 10, 2019 (original 9/25/2012)