By our very nature, hackers tend to get on the bandwagon of new technology pretty quickly. When something gee-whiz comes along, it’s folks like us who try it out, even if that means climbing steep learning curves or putting together odd bits of technology rather than waiting for the slicker products that will come out if the new thing takes off. But building your own television receiver in 1933 was probably pushing the envelope for even the earliest of adopters.
“Cathode Ray Television,” reprinted by the Antique Valve Museum in all its Web 1.0 glory, originally appeared in the May 27, 1933 edition of Popular Wireless magazine, and was authored by one K D Rogers of that august publication’s Research Department. They apparently took things quite seriously over there at the time, at least judging by the white lab coats and smoking materials; nothing said serious research in the 1930s quite like a pipe. The flowery language and endless superlatives that abound in the text are a giveaway, too; it’s hard to read without affecting a mental British accent, or at least your best attempt at a Transatlantic accent.
In any event, the article does a good job showing just what was involved in building a “vision radio receiver” and its supporting circuitry back in the day. K D Rogers goes into great detail explaining how an “oscillograph” CRT can be employed to display moving pictures, and how his proposed electronic system is vastly superior to the mechanical scanning systems that were being toyed with at the time. The build itself, vacuum tube-based though it was, went through the same sort of breadboarding process we still use today, progressing to a finished product in a nice wood cabinet, the plans for which are included.
It must have been quite a thrill for electronics experimenters back then to be working on something like television at a time when radio was only just getting to full market penetration. It’s a bit of a puzzle what these tinkerers would have tuned into with their DIY sets, though — the airwaves weren’t exactly overflowing with TV broadcasts in 1933. But still, someone had to go first, and so we tip our hats to the early adopters who figured things out for the rest of us.
Thanks to [BT] for the tip.
Burried in one of the pages it says the BBC did 4 half-hour test broadcasts a week, so they had to do all their testing and adjustments in that time. So I guess that’s what they watched!
https://www.bbc.com/historyofthebbc/anniversaries/august/first-experimental-bbc-tv-programme
Still better than ITV.
Yes, these modern CRTs suck. Hard.
The good old mechanically scanning tele-vision receivers could be tuned with a tuning fork, just adjust the speed until the vibration from the revolving Nipkow disc (misnamed “spinning disc of death” by some) was in tune with your tuning fork.
Sadly, this simple and sturdy method of receiving tele-vision broadcasts when “high definition tele-vision” became all that of a hype.
And HDTV was, back in the days, anything better than 30p. There were competing standards, like the Baird 240p system (mechanical, of course) or the Marconi-EMI 376i (even though marketed as 405i). Now, the Marconi-EMI system was no longer mechanic, but the ingenious idea was to sync the frame rate with the main power line frequency (which was also 50Hz in the UK), so while you could no longer tune your tele-vision receiver with a tuning fork, the mains frequency could be used for that.
The Marconi-EMI was also famous for allowing extremely large screen sizes by employing a spot wobble oscillator. Enormous 15″ screens were available for the lucky people who could afford this insane luxury!
What no spinning lens filled disk [ of death ] ?
It’s always nice to find little websites like this, with a slice of history. A deceptively simple circuit. Recreating it now, finding parts would no doubt be tricky. Not that there’s anything to watch, short of making a transmitter to go with it. Although I’m not sure how well it would receive a simple signal booster plugged into the rf out of an old vcr. No doubt something would need to be hand crafted. You could almost bitbang a tv signal for this as you would for am radio, with just a wire on an io pin.
I like the irony of the question are “CRT’s safe” with regard to X-Rays … along side someone smoking a pipe. We were not just told tobacco was safe but that it was good for you.
Their simplified explanation isn’t correct and the acceleration voltages used would have produced levels of x-rays that are not considered safe today.
But don’t worry too much, when they became common the tubes were made with lead glass. The lead would absorb x-rays as no one cold agree on what level is safe and how to measure it accurately.
“Four out of five doctors who smoke, smoke Camels”
You gotta love tobacco company marketing. (sarcasm)
No joke: Obviously I’m pretty old, but I remember in the early 1960’s my pediatrician casually knocking the ashes off of my head while telling my mother that she was a hypochondriac.
“the acceleration voltages used would have produced levels of x-rays that are not considered safe today”
No. It used less than 1 kV acceleration voltage: Any ‘X rays’ produced would barely qualify as such, and wouldn’t make it through a millimeter of glass. In the article’s own words: the X rays “are so soft as to fail to pierce even a few inches of air,”
At the 25 kV used in a more modern colour CRT, yes, leaded glass is justified. That’s approximately the voltage used in x-ray mammography systems.
I read 100,000 to 150,000 volts and thought that would definitely generate x-rays. They were referring to x-ray rather than CRT.
If you put it in the context of the time, few if anyone would have built it. It was the depression, I assume that was a concern in the UK. Most hams, and that was probably still the total of “electronic hobbyist”, was using a single tube regen receiver and a simple transmitter, likely CW. Few were prepared to tackle a comlicated project (and yes, way more might have tried the mechanical spinning wheel system). Parts were expensive, bulky, and metalwork needed for the chassis
Yes, there were some who’d build something like this. But endlessconstruction articles in lots of magazines every month were not meant for many to follow along. People built things, they wrote abkut them, and it wasn’t carefully designed to be an optimum design and carefully designed for others to follow exactly. Projects like this extended the horizon, stimulate the brain, and had value even if nobody built it.
Do not underestimate the ingenuity and determination of those early hams. Amateurs were at the forefront of technology, often inventing and experimenting with things well before they became commercially available.
I knew a ham back in the 1960’s that still had some of his 1930’s gear. It was far more elaborate and advanced than a regen receiver and one-tube transmitter. He was making worldwide DX contacts well before WW2.
Most of his gear was heavily modified or home built. Among it was a homebuilt TV receiver AND transmitter. It was a “flying spot scanner” that used an oscilloscope tube to both receive and send images. To send an image, you had the CRT scan a blank raster, placed a slide in front of the CRT, and picked up the light that passed through the slide with a phototube. This was converted to audio, so it could be sent over a regular voice bandwidth.
When you don’t have much, make the most of what you have!
On this of the planet Farnsworth was still perfecting his ideas. And his ideas made it work for many years.
If you’re interested in this early tv tech you need to visit the early tv museum http://www.earlytelevision.org/
In Hilliard Ohio or the Texas Tv museum in Kilgore Texas. Both are incredible museums run as a labor of love by private individual long time collectors. The first museum has many operational sets starting from flying spot mechanicals up to color (also mechanical). The second is housed in a privately purchased car dealership building and has a privately restored early ESPN truck, an early Dumont truck and tons of cool radio, tv etc from earlier days. Both have videos on YouTube. The first has monthly zoom meetings with presentations and a spring convention coming up in a few weeks.
It’s great to go to these museums and listen to the passionate tour guide tell you about old tech.
And so does the American Museum of the Moving Image. And the one at InfoAge.
The Early Television Museum in Columbus, Ohio has a link to this article from the June 1939 issue of Radio News, “Do Hour Own Televising.” The system uses a Nipkow disk transmitter and an all electronic receiver with cathode ray tube.
https://www.earlytelevision.org/pdf/Radio-News-1939-06_do_your_own_televising.pdf
Somewhere I still have a magazine from my grandfather with an article on installing a color wheel synchronized to the horizontal refresh to convert a b/w tv to color
About 1971, they were still playing with that. I remember an article in Electronics Illustrated about a panel that fitted to a tv set. It was a new development or product. Somehow I’mthinking LCD was involved but I don’t know why.
From what I remember it had a chassis of tubes motors and a pair of transparent color stripes on transparent plastic that scrolled across fast.
Jean Shepherd told a great story about very early homebrew television. I’d like to get more info on this project and on the builder, John Anderson W9YEI. EXCELSIOR! 73 Bill
https://soldersmoke.blogspot.com/2022/04/early-television-jean-shepherd.html
The hoops I’ll have to jump through IF I can eventually get my 480 content (loads of well produced and pressed DVDs in my collection before I began buying titles only on 1080p BluRay) to look anywhere near as good on my 50″ plasma as they do on my 32″ Toshiba CRT TV. JRiver player’s Jinc scaler, or if too many artifacts madVr with it’s steeper learning curve, and a beefier graphics card and better cooling/fan noise scheme than originally planned-otherwise a probably much unaffordable Lumagen box.