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.
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.
2 comments here:
It’s important to remember that the acronym NTSC stood for Never Twice the Same Color.
Back in the day most feeds were network or film as videotape was rare and expensive. During times of programming interruptions, it was common to have a camera pointed to a printed card that showed “Please Standby” or some such and the TV stations would play some neutral instrumental music in the background. Add that to the anti establishment attitudes in the 70’s (don’t trust anyone over 30) that low paid video operators had and you got the “Please Standby” card with instrumental music that nobody really recognized but in the town where I lived was an instrumental version of Frank Zappa’s “I am the slime from the video”. It was hilarious. The operator would have been fired on the spot if found out but the station management let it go on for years because they were clueless.
No, “Never Twice (the) Same Color” was derogatory title made by detractors after the fact.
Correct. and the Frank Zappa song was also a derogatory song by detractors after the fact.
In actuality, considering all things, when the lighting was right, cameras were set up properly and the monitors were set up with the proper saturation and contrast and the SMPTE color bars were properly set up in the boxes, the picture looked pretty impressive. Biggest variation was more the setup of the receivers and CRTs in the public’s TV sets. The majority of people I knew saying ‘never twice same color’ were fellow broadcast engineers as an inside joke.
You could also make AM radio sound pretty good too, but that is another story. (although similar)
Both of these are lost technologies.
NTSC = National Television Standards Committee. PAL = Phase Alternate Line. The signal phase is switched every other line to cancel out things like drifting and colour shifts. The added circuitry (especially in the vacuum tube era) made the equipment cost more so people called it Pay for Added Luxury.
The French developed system, SECAM = système électronique couleur avec mémoire, electronic color system with memory. AKA System Essentially Contrary to American Method.
Didn’t the Japanese or Chinese circumvent Telefunken’s PAL patent by producing PAL TVs that essentially consisted of two NTSC decoders?
I’m sorry if it’s not correct or incomplete, but I vaguely remembered reading something like that.
If there’s some truth within however, it would be funny. I mean, NTSC just being half a PAL system. :)
Yes – Sony’s early PAL-compatible Trinitrons avoided any use of the patented Phase Alternation to avoid paying Telefunken. AIUI they used a delay line to repeat the previous line’s chroma (so no phase alternation), and thus created a pseudo-NTSC signal instead. It also meant that Sony ‘PAL compatible’ receivers didn’t benefit from the phase error cancellation that both Simple and Delay Line PAL decoders had.
This is why Sony’s early colour Trinitrons sold for PAL viewing had a Hue/Tint control – which wasn’t ever needed for full PAL decoders.
(Simple PAL decoders had Hanover bars on phase errors – which the eye/brain averaged at viewing distances common at the time. Delay line PAL decoders averaged two lines of chroma, and the alternate line phase alternation meant that phase errors thus became the far-less obvious desaturation, not hue rotation, error)
No. NTSC = National Television System Committee
In the sixties I remember very grainy reception of US channels, which disappeared when the adjacent local channels came on. I don’t think I ever saw a full episode of Captain Kangaroo.
Worse, the local stations were just warming up. So a period of test patterns rather than programming. TV went off the air each night.
WTLA now concludes its broadcast day.
Ooh say can you see …
pshshsshshhshshsh…
The one station out of our area that was aired on our cable back then in the 60’s signed off with the lord’s prayer signed in Native American sign language by a silent Indian in full dress in a natural setting.
We’d have a houseful of neighbors over to watch “Uncle Miltie” on a 10 inch screen with a magnifier in front of it.
I miss being able to receive my TV signals year around before digital transmissions. Digital transmissions don’t make it to my home except for a few days a year when the weather is clear and the trees have all lost their leaves. Surprising since I live inside the metro area of the fourth most populated city in the U.S. If my internet goes down, I have no television at all now.
Digital signals don’t bounce and reflect as well as analog. Well, they do bounce but it tends to so severely scramble the data that the receiver ignores it as though it’s not there.
You need to raise your antenna up a lot higher, preferably above the trees. If you get a lot of lightning then you’ll want a lightning rod next to the antenna, and taller than it, plus a lightning protector in the cable to the antenna.
That’s the case with the US 8VSB ATSC Digital OTA system – but it isn’t the case to the same degree with the DVB-T/T2 COFDM OTA systems, which are far less sensitive to multi-path/reflections – and in fact can use it to their advantage. (It may be why ATSC 3.0 uses a lot of similar tech to DVB-T2)
This allows DVB-T/T2 to operate ‘Single Frequency Networks’ where it’s fine to receive signals from more than one transmitter carrying the same service on the same frequency. https://en.wikipedia.org/wiki/Single-frequency_network#DVB-T_SFN
From the Transmitter antenna to the receiving antenna it’s all analogue. Digital signals don’t exist at that point. Before it leaves the transmitter it is digital, through the air it is analogue, in the TV it get converted back to digital.
Digital over-the-air is definitely not as forgiving as analog. The current standard has an issue with “multipath” – which is if you receive multiple copies of the signal at slightly different times due to reflections and such. It doesn’t take much multipath interference to render the signal useless, and a mistake often made by folks is to get a bigger antenna or amplify the signal even if they are near the transmitter. This usually makes it worse because the antenna and amplifier act on the reflected signals just like the primary.
If you live downtown you might try using a lower gain antenna and see if that helps.
Slightly different times = different phase. This is the problem that PAL solved so that VHF signals could travel several hundred kilometres.
“If my internet goes down, I have no television at all now.”
Don’t worry, you aint missing much!
B^)
Yep I remember good old analogue. I do miss it even though I have a digital antenna.
I don’t have an analog TV,
I should have kept one for the Timex-Sinclair 1000 and the Mattel game console.
You don’t have a “digital” antenna. ATSC and other digital broadcast TV is still using the same analog frequencies (except for low VHF which has been repurposed) as before. The signals are done like how dialup modems were used to send data over analog phone lines.
In most places in the USA a UHF antenna will get all the ATSC broadcasts. Unless there are stations broadcasting ATSC in the high VHF band you can use an antenna with no VHF elements.
It doesn’t even have to be a particularly good antenna if you have a good line of sight to the transmitter. I have a beat up and decades old, foldable RV antenna on my roof that gets over 40 ATSC channels. The mechanism that unfolded and rotated it from inside the RV it was on was broken so I unfolded it and permanently fixed it in place. Some of the elements were a bit bent so I just bent them back pretty close to straight.
It has a pair of screw posts to attach a flat twinlead so I attached a balun to convert to coaxial cable. Didn’t’ cost me a cent since I already had the balun and coax to go with the free antenna.
There’s a big old 1950s era telecom building near where I live that still has a set of giant long-obsolete microwave horns in the tower above it. I need to get a picture before they remove them.
Do you remember this HaD article?
https://hackaday.com/2017/07/10/horns-across-america-the-att-long-lines-network/
Alternate title: “How Television Worked In The 1950s – In North America” :)
Also, France had developed an 819 line system in 1949 that was on air up until 1985.
https://www.liquisearch.com/analog_high-definition_television_system/french_819-line_737i_system
I’d suggest that it’s important to appreciate that the original composite video standard, not to mention PAL/NTSC etc. which were basically derivatives, was designed primarily to minimise receiver complexity. As a result, designs like https://www.cool386.com/5BP1/rsz_1dscf1690a.jpg (from https://www.cool386.com/5BP1/5%20inch%20TV%20receiver.html) had a mere couple of dozen active components.
it was in fact common to see construction articles detailing how to repurpose RF and IF electronics from military receivers: not unlike the way that early computer hobbyists salvaged commercial keyboards etc.
When TV transmissions resumed in the UK in the late 40s, there was apparently a residential course offered to one teacher per county during which attendees would build a TV receiver. My grandfather, an experienced wireless tinkerer, was apparently very disappointed not to be selected on behalf of Denbighshire, since he would very much liked to have presented a TV to the school at Pentre (near Chirk) on his retirement as schoolmaster.
Bigger antennas are usually more directional. There’s an improved chance of the ratio of direct to reflected signal strengths being higher, and a good chance of putting the strongest reflected signal into a null.
The title should probably be “How Analogue TV Works”, with no reference to the 1950s, seeing as it still works exactly the same in 2022 where it’s still broadcast. A quick look at Wikipedia shows that many countries still do.
https://en.wikipedia.org/wiki/Digital_television_transition#/media/File:Worldmap_digital_terrestrial_television_transition.svg
One example is the United States, which still broadcast analogue TV in 2022.
https://docs.fcc.gov/public/attachments/FCC-21-78A1.pdf
Here’s my question.
I understand the camera and scanning and sending that info over the air and tv reception and all that.
BUT, when a movie was shown, how was the movie gotten into the camera? Was it shown on a screen and the camera saw that and sent that into the airwaves?
I have no idea!