April 1960 Popular Electronics
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Popular
Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged. See all articles from
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. The
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.
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
B&W photo of PAR display showing Elevation display at top and
Azimuth display on bottom. Yes, it is in dire need of alignment.
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.
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