A Small Dose of Whimsy
There was a DXer named Phil
Who craved a test of his skill.
He made a stacked rhombic beam
To fulfill his big dream
Of DX from Seville to Brazil.
The Discovery of Direct View Storage Technology
You’ve probably all seen a conventional analog oscilloscope display, where an electron beam traces out a wave on the screen. If the wave repeats itself, you get the illusion of a stationary graph of voltage as a function of time. But what if the wave does not repeat? How do you capture and analyze the display?
The modern solution is to digitize the signal and store it in RAM. But that solution did not exist in 1969, when I started working at Tektronix. So what were the alternatives? One choice was an oscilloscope camera and Polaroid film. That works, and will capture fast events, but it’s expensive. Another choice was the direct view storage tube. You write on the phosphor, and the screen stays written until it is erased. That is very cool. And that is what Tektronix did. It gave rise to the 564 storage oscilloscope, which was very popular.
But how did this all start? It was an accident.
The front part of a cathode ray tube is called the funnel. Sometimes it’s a single piece of glass, and sometimes it is a ceramic funnel with a flat faceplate secured by frit, sort of the ceramic equivalent of solder. The funnel receives a liquid that contains the phosphor, which precipitates out on the face of the tube. The funnel is then very gently tipped, decanting off the remaining liquid. Aluminization is usually added, then the funnel is joined to the electron gun, the whole assembly is evacuated, and you have a complete cathode ray tube.
Running the phosphor settling operation was the job of Joe Coulomb. And one day the process went a little bonkers. When the resulting tubes were taken to CRT Test, whatever trace was written on the tube face simply remained. John Whitesides, who ran the test department was very busy taking these tubes across the street to the oscilloscope assembly plant, where he found that the trace remained even after walking across the campus.
So direct view storage wasn’t so much invented as it was discovered. The development of the associated products consisted of finding out where the phosphor settling process went wrong, duplicating the effect, and figuring out how to erase it.
The next fun step happened at the Mayo Clinic in Rochester, MN. They took a 564 oscilloscope and replaced the time base plug-in with a second vertical amplifier plug-in. This produced a storage XY monitor that they used for physiological measurements. Just for perspective, at about this time I paid $128 for 32K of static RAM. Direct view storage was much cheaper and produced higher quality graphics.
Tektronix thought that was pretty slick, and developed the 4010 graphic terminal and the 4051 computer, running BASIC. RAM was expensive, A-D converters were slow, and Tektronix’ direct view storage was a better, cheaper solution. At one time, we had 85% of the world’s computer graphic market. My kids played Pong, Star Trek, and Artillery on a 4051, and learned a small bit of BASIC programming on one. If you saw the original version of Battlestar Gallactica, you might remember Adama using one to generate a report.
One day, I walked into an electronics store in a Beaverton mall, and there was a computer running Pong on a conventional video monitor. At that moment, I knew that the jig was up, and direct view storage computer displays were doomed, and that was sadly true. But it was wonderful, lucrative fun while it lasted.
73 for now,
Denton