Retrotechtacular: The Forgotten Vacuum Tube A/D Converters Of 1965

June 8, 2022 by Dan Maloney 13 Comments

In any era, the story of electronics has very much been about figuring out how to make something happen with what’s available at the time. And as is often the case, the most interesting developments come from occasions when needs exceed what’s available. That’s when real innovation takes place, even if circumstances conspire to keep the innovation from ever taking hold in the marketplace.

This gem of a video from the Antique Wireless Association has a perfect example of this: the long-lost analog-to-digital converter vacuum tube. Like almost every mid-20th-century innovation in electronics, this one traces its roots back to the Bell Laboratories, which was keenly interested in improving bandwidth on its massive network of copper lines and microwave links. As early as 1947, one Dr. Frank Gray, a physicist at Bell Labs, had been working on a vacuum tube that could directly convert an analog signal into a digital representation. His solution was a cathode ray tube similar to the CRT in an oscilloscope. A beam of electrons would shine down the length of the tube onto a shadow mask containing holes arranged in a “reflected binary code,” which would later be known as a Gray code. The analog signal to be digitized was applied to a pair of vertical deflector plates, which moved the beam into a position along the plate corresponding to the voltage. A pair of horizontal deflector plates would then scan the beam across the shadow mask; where electrons fell on a hole, they would pass through to an output plate to be registered as a bit to be set.

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Retrotechtacular: Clay Pipe The Hard Way

May 31, 2022 by Dan Maloney 28 Comments

Troll YouTube long enough and chances are good that you’ll come across all kinds of videos of the “How It’s Made” genre. And buried in with the frying pans and treadmills and dental floss manufacturers, there no doubt will be deep dives on how pipe is made. Methods will vary by material, but copper, PVC, cast iron, or even concrete, what the pipe factories will all have in common is the high degree of automation they employ. With a commodity item like pipe, it’s hard to differentiate yourself from another manufacturer on features, so price is about the only way to compete. That means cutting costs to the bone, and that means getting rid of as many employees as possible.

Such was not always the case, of course, as this look at how Irish Stoneware & Fireclays Ltd. made clay pipe, drain tiles, and chimney flues back in the 1980s shows. The amount of handwork involved in making a single, simple piece of clay pipe is astonishing, as is the number of hands employed at the various tasks. The factory was located in Carrickmacross, County Monaghan, Ireland, near an outcropping of shale that forms the raw material for its products. Quarrying the shale and milling it into clay were among the few mechanized steps in the process; although the extrusion of the pipe itself was also mechanized, the machines required teams of workers to load and unload them.

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Retrotechtacular: How Television Worked In The 1950s

May 6, 2022 by Jenny List 29 Comments

Watching television today is a very different experience from that which our parents would have had at our age, where we have high-definition digital on-demand streaming services they had a small number of analogue channels serving linear scheduled broadcasting. A particular film coming on TV could be a major event that it was not uncommon for most of the population to have shared, and such simple things as a coffee advert could become part of our common cultural experience. Behind it all was a minor miracle of synchronised analogue technology taking the signal from studio to living room, and this is the subject of a 1952 Coronet film, Television: How It Works! Sit back and enjoy a trip into a much simpler world in the video below the break.

Filming a TV advert: 1950s housewife sells cooker — Production values for adverts had yet to reach their zenith in the 1950s.

After an introduction showing the cultural impact of TV in early-50s America there’s a basic intro to a cathode-ray tube, followed by something that may be less familiar to many readers, the Image Orthicon camera tube that formed the basis of most TV signals of that era.

It’s written for the general public, so the scanning raster of a TV image is introduced through the back-and-forth of reading a book, and then translated into how the raster is painted on the screen with the deflection coils and the electron gun. It’s not overly simplified though, for it talks about how the picture is interlaced and shows how a synchronisation pulse is introduced to keep all parts of the system working together.

A particularly fascinating glimpse comes in a brief mention of the solid copper co-axial cable and overland microwave links used to transmit TV signals across country, these concrete towers can still be seen today but they no longer have the colossal horn antennas we can see in the film.

A rather obvious omission in this film is the lack of any mention of colour TV, as while it would be late 1953 before the NTSC standard was formally adopted and early 1954 before the first few colour sets would go on sale. Colour TV would have been very much the Next Big Thing in 1952, but with no transmissions to watch and a bitter standards war still raging between the field-sequential CBS system and RCA’s compatible dot-sequential system that would eventually evolve into the NTSC standard it’s not surprising that colour TV was beyond the consumer audience of the time.

Thus we’re being introduced to the 525-line standard which many think of as NTSC video, but without the NTSC compatible colour system that most of us will be familiar with. The 525-line analogue standard might have disappeared from our living rooms some time ago, but as the last few stations only came off-air last year we’d say it had a pretty good run.

We like analogue TV a lot here at Hackaday, and this certainly isn’t the first time we’ve gone all 525-line. Meanwhile for a really deep dive into the inner workings of TV signal timing, get ready to know your video waveform.

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Retrotechtacular: The Power To Stop

April 23, 2022 by Dan Maloney 22 Comments

In everyday life, the largest moving object most people are likely to encounter is probably a train. Watching a train rolling along a track, it’s hard not to be impressed with the vast amount of power needed to put what might be a mile-long string of hopper cars carrying megatons of freight into motion.

But it’s the other side of that coin — the engineering needed to keep that train under control and eventually get it to stop — that’s the subject of this gem from British Transport Films on “The Power to Stop.” On the face of it, stopping a train isn’t exactly high-technology; the technique of pressing cast-iron brake shoes against the wheels was largely unchanged in the 100 years prior to the making of this 1979 film. The interesting thing here is the discovery that the metallurgy of the iron used for brakes has a huge impact on braking efficiency and safety. And given that British Railways was going through about 3.5 million brake shoes a year at the time, anything that could make them last even a little longer could result in significant savings.

It was the safety of railway brakes, though, that led to research into how they can be improved. Noting that cast iron is brittle, prone to rapid wear, and liable to create showers of dangerous sparks, the research arm of British Railways undertook a study of the phosphorus content of the cast iron, to find the best mix for the job. They turned to an impressively energetic brake dynamometer for their tests, where it turned out that increasing the amount of the trace element greatly reduced wear and sparking while reducing braking times.

Although we’re all for safety, we have to admit that some of the rooster-tails of sparks thrown off by the low-phosphorus shoes were pretty spectacular. Still, it’s interesting to see just how much thought and effort went into optimizing something so seemingly simple. Think about that the next time you watch a train go by.

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Retrotechtacular: A DIY Television For Very Early Adopters

April 10, 2022 by Dan Maloney 21 Comments

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.

Retrotechtacular: The Transatlantic Radiotelephone System Of The 1930s

April 2, 2022 by Dan Maloney 8 Comments

With the web of undersea cables lacing the continents together now, it’s hard to imagine that it wasn’t until 1956 that the first transatlantic telephone cable was laid. Sure, there were telegraph cables under the Atlantic starting as early as the late 1800s, but getting your voice across the ocean on copper was a long time coming. So what was the discerning 1930s gentleman of business to do when only a voice call would do? He’d have used a radiotelephone, probably at an outrageous expense, which as this video on the receiving end of the New York to London radio connection shows, was probably entirely justified.

The video details the shortwave radiotelephone system that linked New York and London in the 1930s. It starts with a brief but thorough explanation of ionospheric refraction, and how that atmospheric phenomenon makes it possible to communicate over vast distances. It also offers a great explanation on the problems inherent with radio connections, like multipath interference and the dependency on the solar cycle for usable skip. To overcome these issues, the Cooling Radio Station was built, and its construction is the main thrust of the video.

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Retrotechtacular: Measuring TV Audiences With The “Poll-O-Meter”

March 12, 2022 by Dan Maloney 21 Comments

It may come as a shock to some, but TV used to be a big deal — a very big deal. Sitting down in front of the glowing tube for an evening’s entertainment was pretty much all one had to do after work, and while taking in this content was perhaps not that great for us, it was a goldmine for anyone with the ability to monetize it. And monetize it they did, “they” being the advertisers and marketers who saw the potential of the new medium as it ramped up in early 1950s America.

They faced a bit of a problem, though: proving to their customers exactly how many people they were reaching with their ads. The 1956 film below shows one attempt to answer that question with technology, rather than guesswork. The film features the “Poll-O-Meter System,” a mobile electronic tuning recorder built by the Calbest Electronics Company. Not a lot of technical detail is offered in the film, which appears aimed more at the advertising types, but from a shot of the Poll-O-Meter front panel (at 4:12) and a look at its comically outsized rooftop antenna (12:27), it seems safe to assume that it worked by receiving emissions from the TV set’s local oscillator, which would leak a signal from the TV antenna — perhaps similar to the approach used by the UK’s TV locator vans.

The Poll-O-Meter seems to have supported seven channels; even though there were twelve channels back in the day, licenses were rarely granted for stations on adjacent channels in a given market, so getting a hit on the “2-3” channel would have to be considered in the context of the local market. The Poll-O-Meter had a charming, homebrew look to it, right down to the hand-painted logos and panel lettering. Each channel had an electromechanical totalizing counter, plus a patch panel that looks like it could be used to connect different counters to different channels. There even appears to be a way to subtract counts from a channel, although why that would be necessary is unclear. The whole thing lived in the back of a 1954 VW van, and was driven around neighborhoods turning heads and gathering data about what channels were being watched “without enlisting aid or cooperation of … users.” Or, you know, their consent.

It was a different time, though, which is abundantly clear from watching this film, as well as the bonus ad for Westinghouse TVs at the end. The Poll-O-Meter seems a little silly now, but don’t judge 1956 too hard — after all, our world is regularly prowled by equally intrusive and consent-free Google Street View cars. Still, it’s an interesting glimpse into how one outfit tried to hang a price tag on the eyeballs that were silently taking in the “Vast Wasteland.”

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