The Comforting Blue Glow Of Old Time Radio

When you think of an old radio it’s possible you imagine a wooden-cased tube radio receiver as clustered around by a 1940s family anxious for news from the front, or maybe even a hefty 19-inch rack casing for a “boat anchor” ham radio transmitter. But neither of those are really old radios, for that we must go back another few decades to the first radios. Radio as demonstrated by Giulielmo Marconi didn’t use tubes and it certainly didn’t use transistors, instead it used an induction coil and a spark gap. It’s a subject examined in depth by [The Plasma Channel] and [Blueprint], as they come together to build and test a pair of spark gap transmitters.

This is a collaboration between two YouTube channels, so we’ve put videos from both below the break.They both build simple spark gap transmitters and explain the history behind them, as well as running some tests in RF-shielded locations. The transmitters are fairly crude affairs in that while they both use electronic drives for their induction coils they don’t have the resonant tank circuitry that a typical early-20th-century transmitter would have had to improve its efficiency.

They are at pains to remind the viewer that spark gap transmitters have been illegal for nearly a century due to their wideband interference so this is definitely one of those “Don’t do this at home” projects even if it hasn’t stopped others from trying. But it’s still a fascinating introduction to this forgotten technology, and both videos are definitely worth a watch.

13 thoughts on “The Comforting Blue Glow Of Old Time Radio

    1. You bet , early failed attempt at a Tesla coil, I think I was 12 , Lots of sparks (the longest about a foot) till our capacitor bank exploded and filled the room with paper and aluminum foil . Very exciting for about 5 to 10 seconds.
      The lads mother (who’s house we were using) came down stairs and asked what we did to make the TV go “fafas fafas” The next day the DOT ( later the DOC) truck was wandering the neighbourhood looking for us. We did not try that again, though it wasn’t the last time we got the truck to come over ( ferry) from Vancouver.

    1. A full spectrum jammer would require so much power that you would be instantly found through radio direction finding even if your coal power plant to run the thing somehow went unnoticed. There are so many ways around a jammer like this that it would be incredibly useless.

      1. Actually when I was just a kid I wanted to build an alternating flasher with a couple of transistors. I did not have a lot of parts as a kid, so I made um, substitutions. This was back when I had more of the farmer “get it done” and see what happens attitude. Pre any kind of engineering. The RC in the circuit called for a couple of decent sized electrolytic caps that I did not have, but I did have some big ceramic caps, so I used them. When I first powered it up, I thought it did not work as both lights were on all the time. But when I turned the radio on the station it had been tuned to was gone. I tried another, and the dial was dead. I was getting ready to tune to one of the old CD frequencies. I tried the TV with the same effect. Nada. Than, independently of the radio and TV I recalled I left my gadget on. I was more concerned about killing the battery than anything else. But as soon I I removed the battery, the TV came in, and I was able to tune the radio back in again. Hmmm. Put the battery back in, poof, everything gone. I had some fun with that and my friends. If you are near by the receiver, it does not take a lot of power to do a pretty wide band signal jam.

        And as to the main theme, you mean there are people who have never heard of spark gap transmitters? Urg. Than again I see people who can not light up an LED without an arduino.

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