The Good Old Days?
Kirt's Cogitations™ #200

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The Good Old Days?

In the last few years, many things I have read or watched keep reminding me of how fast time is passing and how quickly technology is advancing. One of the most recent examples is while studying a photograph of a modern air traffic control (ATC) radar display. The incredibly large displays (plan position indicators, or PPIs, in ATC parlance) draw razor sharp lines and text characters and perform an amazing repertoire of sophisticated target tagging and tracking functions. Seeing all the many lines outlining terminal control areas, stationary obstacles, terrain features, VOR stations and runway outlines made me think about how relatively easily those maps are generated nowadays using packaged software and a desktop PC. Draw a line and if it doesn't turn out quite right, simply delete it or move it or maybe make it a little longer or shorter. No problemo.

In my days of radar, the maps were manually etched on a circle of glass with a black surface coating, using the equivalent of a pantograph.

Back in my day of working on ATC radars in the U.S. Air Force, when both the surveillance and precision approach systems were still primarily constructed of tube circuits, making area maps was not quite so simple. Crude by today's standards, our analog video mapping system, the AN/GPA-131, used one of the earlier applications of a photomultiplier tube. The air traffic controllers generated maps by etching lines on a small round glass plate that had a thin layer of flat black paint on it. If my memory serves me well, the mechanism they used was similar to a pantograph with a scribe on the end rather than a pencil or pen. Repairing mistakes usually meant trashing the work in progress and starting anew. Making a backup meant going through the painstaking ordeal of manually etching a new plate.

The way the system worked was that a miniature CRT was located on the side of the plate opposite of the photomultiplier tube, and a sweep was generated that was synchronized with the actual radar PPI sweep. The photomultiplier tube recorded the position of the light detected through the etched lines and the resulting analog signal was summed into the raw radar video that was presented to the air traffic controllers. The only electronic adjustments available were rotation and scaling for alignment. It really was quite impressive in its day.

That, of course, is just one example of things that make feel old. The older I get, the more I notice. My only regret is not having had these new technologies available as a starting point back 25+ years ago. BTW, I was born the same year that the Explorer 1 satellite was launched.