The vacuum tube triode was one of the greatest inventions ever. It didn’t abrogate the laws of physics, but it certainly delivered more for less. It was to electronics what the lever, wheel, and screw were to mechanics. It became a ubiquitous building block, often serving multiple purposes at the same time, and it enabled a torrent of inventions.
In laymen’s terms, the vacuum tube transmitter produced beautiful continuous waves, added voice or music, and boosted the signal so it could be heard far away. The vacuum tube receiver picked up weak signals, extracted the speech or music, and made the audio loud.
When I was growing up the vacuum tube was still king. I’ll never forget earning my first ham radio license and building a crystal-controlled, 40-watt transmitter out of parts salvaged from old TVs. I started with a piece of sheet metal, drilled holes for the sockets and switches, and bent the metal into the shape of a chassis. I mounted the parts and soldered the wires. It seemed to work—at least on the workbench. Yet it was hard for me to believe this little contraption could produce CW (Morse code) signals that would be heard 1,000 miles away.
I hooked it up to my antenna and nervously began tapping out “CQ”—the Morse code abbreviation for “calling anyone.” An hour of trying yielded no responses. Was my 4-tube Hallicrafters receiver the problem? Or was my ground-mounted vertical antenna too close to the house? Then I heard someone tapping out my call sign. My first contact was a station in Maryland. (I was living in a suburb of Chicago at the time.) I was thrilled.
Transistors were already starting to replace vacuum tubes. My next “rig” was a kit consisting of both vacuum tubes and transistors. But the writing was on the wall: the vacuum tube was doomed by computers. Vacuum tubes were too big, too power hungry, and too unreliable. Heck, so were discrete transistors. It wasn’t long before they were replaced by integrated circuits.
It’s not the vacuum tubes themselves that I miss. It’s building, troubleshooting, and operating my own equipment. I somehow felt more “connected” to the technology.
The eighth chapter of my book is about Lee de Forest, inventor of the vacuum tube triode, and Edwin H. Armstrong, inventor of the regenerative receiver, the superheterodyne receiver, and frequency modulation--all using vacuum tubes. It’s an inspiring story in many ways, but it’s also a tragedy.
Armstrong learned early on that most people are their own worst enemy. Paraphrasing American humorist Josh Billings, Armstrong’s mantra became: "It ain't ignorance that causes all the trouble in this world. It's the things people know that ain't so." As if to illustrate the point, Armstrong invented frequency modulation (FM) after a respected Bell Labs engineer announced that it wasn’t worth doing. Everyone assumed from the start that FM had to be a narrowband technology. Armstrong discovered FM’s crystal clear audio by ignoring conventional wisdom.
Unfortunately, Armstrong got embroiled in patent disputes that he probably could have avoided. After a string of defeats in court, the man who used to get a thrill climbing antenna towers jumped out of his 13th story window to his death. Ironically, his wife (who had tried to dissuade him from continuing the patent fight) took up the cause and managed to overturn two major court decisions, vindicating her late husband.
Next time: David Sarnoff—high tech business genius or SOB?