Reviving Teletext for Ham Radio | Hacker News Reader

Reviving Teletext for Ham Radio

spectrum.ieee.org

72 pointsyarapavan45 comments

One of the ironies of a vibe coded VHF teletext is that the LLM-pocalypse prompted dropping low-level network support (AX.25) from the Linux kernel, which is the basis of a lot of ham networking experiments.

There are userspace workarounds for much of what was dropped, there were no real upstream maintainer of this stuff, and it was justifiable to drop AX.25 support. I don't really understand any of it, nor am I in the unenviable position of keeping it around/working. But a real mixed bag of ham news, AFAICT.

I didn't see it got dropped, that is very unfortunate but also understandable. It's been a few years since I last messed around with it. If I recall, what was in the kernel at the time had a few issues and hadn't been touched in a very long time. It was a huge hassle to get working, there wasn't much up to date documentation.

I made back images and kept a lot of the documentation in case I needed to go back since it was tricky to find the first time.

However once you do get it working it's very satisfying to see a connection through a VHF radio appear in the native linux networking stack. Opens doors to a lot of goofy and fun ideas.

That brings back fond memories of my first employer in the early 90s.

They used to rent a single scan line (VBI) of the TV broadcast to use as a data transmission method encoded the same way Teletext was. IIRC you could fit 45 bytes in a single scan line, with 50 per second that gives you a nationwide data broadcast capability of something like 18 kbit/s. We had a 19,200 bits/second leased line to send the data.

That scan line was really really expensive I seem to remember! If your TV wasn't quite adjusted properly you could see the data scan lines at the top of the screen as flickering white dots and lines which was fun.

The data got sent to financial institutions for real time stock feeds and nationwide networks of shops.

I never worked on the code for that part of the business though - I worked on the replacement system which ran via satellite with much more bandwidth at much lower cost.

Eventually the internet killed that too :-)

I love learning about pre-internet ways of transferring data on the back of other things. Another cool example is that the UK is only shutting down its longwave AM radio service this month (as opposed to decades ago) because the carrier is phase-modulated with data telling older electric meters to switch over. For years this was the only reason such an antiquated radio system stayed alive.

> I love learning about pre-internet ways of transferring data on the back of other things

See Minitel from France and Telidon from Canada as other examples of data systems riding on analogue TV and/or POTS telephone systems.

I love learning about pre-internet ways of transferring data on the back of other things.

I once worked for a radio station that made 90% of its revenue from carrying data feeds on subcarriers, and not from main music programs.

Because of the geographic location and size of the signal, it was a vital link between two major cities before planting fiber optic lines became cheap.

I’m looking forward to cell phones un-shackling themselves from telecom oligopolies through a mix of repurposed satellite uplink and where available: some FM spectrum downlink utilization.

Just stream me the weather, traffic, text msgs & some news stories that a TTS can read out to me.

Won’t work well for streaming a video but for most of us generally on wifi except out-of-doors, I can live with it.

Just stream me the weather, traffic, text msgs & some news stories that a TTS can read out to me.

SiriusXM is half way there. It supplies weather and traffic as a data service.

I knew about traffic from way back when the service was new, and found out Sirius Marine Weather a few years ago, but recently rented a car that also had Sirius-delivered weather and traffic alerts.

It was very useful as I was deeply off the grid (no radio stations at all during the day and AM skywave only at night), and the car alerted me to nearby lightning and thunderstorms that I couldn't see because of the terrain.

In Munich (Germany), a lot of the displays at bus and tram stations get their data via a side leg on the FM radio broadcast of local station B5 aktuell [1]. More details are here [2], apparently it's called "Axentia iBus FM/DARC".

[1] https://www.mikrocontroller.net/topic/232846

[2] https://apollo.open-resource.org/mission:log:2014:08:08:darc...

Up here in the north of Scotland the various council water and drainage departments often had to send data from remote data loggers (high tech stuff in the early 80s). Some of them would transmit a little ping of data every few seconds and if it heard a reply it would send several bursts of data quickly, using meteor scatter[1] to get it back to the receiving station hundreds of miles away.

All gone now, it's all 4G.

A few hours drive north of me is Mormond Hill, formerly the site of one part of the North Atlantic Radio System[2]. This used tropospheric scattering and huge dish aerials to communicate radar data down to RAF Fylingdales. There's not much up there now. There were various BT microwave links for offshore oil installations and assorted UHF and VHF links up, but the masts are pretty bare now.

[1] https://en.wikipedia.org/wiki/Meteor_burst_communications

[2] https://en.wikipedia.org/wiki/North_Atlantic_Radio_System

You should check out the Media Archeology Lab, they are very interested in alternate networks of all types! https://www.mediaarchaeologylab.com/

They used to rent a single scan line (VBI) of the TV broadcast to use as a data transmission method

In the days before cable TV was widespread, there were over-the-air devices to give you a "TV Guide" page, like your cable/satellite service does now.

It was a tiny gray box about the size of a VHS tape, with a cute antenna sticking out of the top.

It constantly received program listing data through scan line data services, and filtered the listing by your ZIP Code. It displayed its TV Guide page on channel 3 or 4, and passed through the rest of the spectrum from your antenna. Because of this, it could even switch channels for you.

It cost something like $40, and after that was a totally free service, with no advertisements.

I'm pretty sure I got mine at Radio Shack, so it's probably listed in the catalogs around 1994 or so.

> If your TV wasn't quite adjusted properly you could see the data scan lines at the top of the screen as flickering white dots and lines which was fun.

There was a stock fault on BRC 1400 series valve TVs where a resistor in the brightness network would drift high in value and cause uncontrollable bright flyback lines in the upper half of the screen, and you could see those wriggly dotty crawlies ;-) I can't remember the component number - I think I last replaced one when I was 15 or 16, they were the teenage bedroom hand-me-down set of choice in the 80s, absolutely scads of them about in all sizes - but I can still picture in my mind's eye exactly where on the board it is, 220kΩ, red red yellow.

All long gone now, I expect.

If you find one do not re-cap it - the capacitors will be fine. They always are, there aren't any tantalums in it. Instead pay attention to everything above about 200kΩ and find out which ones are now closer to 1 meg!

This Teletext emulator displays a few projects recreating various services: https://zxnet.co.uk/teletext/viewer/.

I'm planning on building my own Teletext service at some point as part of a wider analogue TV project. It's a cool form for things like the news because you have to be very concise for it to work in such a constrained format; it's the opposite of today where long-form content that doesn't really say anything is dirt cheap to emit at scale. Some of the British services had rudimentary games too like Bamboozle, a quiz game which relied on hexadecimal pages the remote couldn't enter manually.

One thing I'd also like to reinstate is NICAM digital stereo which British analogue TV used to have, most modulators I've come across only generate a mono FM subcarrier in PAL mode so looks like I'm going to be building my own modulator.

Please consider framing your project in your mind as a hobby. It’s valuable to the degree that you enjoy it. Learning and other external values don’t have to apply here. Just the fun of doing it can be enough.

Ham radio as a whole is a great hobby to sink your random RF projects into already.. its a hobby within a hobby, no matter what path you may take ;)

I'm familiar with the author's past work on ieee.org and have a sense that he likes to write to/for both hobbyist and professional camps:

https://spectrum.ieee.org/u/stephen-cass

You have me pegged correctly :)

This is fantastic, the article and the implementation, it looks really good. I have been working on a BBS client lately, and Teletext was also on my maybe wishlist for one day. I also dabble with radio, not HAM though, im not licensed. So i'm still a CB radio supporter.

Maybe I’m getting senile, but the article lacks even the tiniest amount of detail and contains no link to the implementation. I found also nothing on the intarweb about it, other than this article and a few clones of it. I wonder if this is real at all. It’s an IEEE article, so it should be. But I find this lack of detail very depressing.

Thanks, I thought I was going crazy but yeah, I feel the same way. There are soooo many links in the article, and they're almost entirely irrelevant. It feels like browsing the web with adware installed on your computer in the early 2000s

Original article author here: There's isn't anything on the wider web about this project because it is a bespoke creation for IEEE Spectrum's Hands On column! If you're not familiar with the column, it's always written at a pretty high level. That said, I will be putting all the code up on a public repo, once I get a chance (hopefully very soon!) to verify a cold install on a fresh machine does work.

Thanks! To be clear, it’s totally fine to write articles like this, obviously. I just felt that some who goes above and beyond on such an esoteric subject would be vibrating with energy to share as many details with likeminded enthusiasts:)

If I had more time, I’d like to play with this (and trying to recreate an old style stand alone tnc for packet radio) :)

I'm normally pretty good about writing close to length, but the first draft of this 950-word article was over 2,000 words long. :) I only get three pages per issue though, so even though sometimes it's painful deciding what lore to leave out, it has to be done :)

This is just me, but I would have written the 2000 word article, and made it it a md file on github as future home of the code you're going to drop. Then link it from the 950 word IEEE article. Then you'd already have a crystallization point for future work.

I think you had 999 pages but each page could have 9999 sub pages.

The pages were send one by one so if you typed 200 you would have to wait for page 200 to cycle by. If it had 100 sub pages you would have to wait 100 times as long. I believe more important pages could be send more often or similarly the cycle would skip less important pages. Decent TV's would just store pages and sub pages until the next cycle.

I asked crappy local TV stations what a page would cost but they didn't have anything under 1500 guilders per month (comparable to $1500 today) which was an absurd amount of money for 1kb of hosting.

No wonder that, besides news, subtitles and the tv guide, the thing was entirely filled with lottery phone lines, astrology lines, sex lines and similar trash.

Viewing the fee as being for a volume of storage doesn't seem the right perspective. It's $1500 to lease some %age of spectrum for some period. If true Teletext on an analogue signal and broadcast vs cable, then $1500 for 0.05% of the total non-media spectrum doesn't feel like a terrible deal.

$1500 today is probably in the region of 10s of GB, sure, but that's almost a commodity volume by comparison in terms of supply.

The way I thought of it at the time was that they had 2 kinds of content, official stuff like news, to make the service actually useful, for which they didn't get a cent and commercial stuff which started at that unfunny amount. They had nothing in between.

For example, I could have made a page with sub-pages with the menu from various restaurants in town. It didn't occur to me that one could monopolize delivery and squeeze restaurants into handing over a large amount of money per meal. (read: cut a large amount of food) I'm not that kind of entrepreneur. I'm sure they do actually pay ƒ1500 now for a dumb listing on a food delivery website. I thought of it as more of a fun thing to have for the local tv station (that hardly anyone watched)

I was just fooling around really but my main plan at the time was classifieds. The normal formula for those at the time was to deliver the text some place and pay in cash. I had considered a paid phone number but those also cost 1500 + 50% of the call cost. A 3 minute call would work out to cost 3 bucks of which I would get ƒ1.50 and I would need 1000 per month just to pay for the phone line. Absurd prices, local (land line) calls at the time cost 10 cents each for unlimited duration and 35 guilders every 2 months.

For a TV station with less than 100 k "viewers" I don't expect many thousands of classifieds. It wouldn't even fit on the page. Say you can fit 10 of them. Say 300 one day ads per month. As a customer, I wouldn't pay ƒ5 per day. The local newspaper started at ƒ6 and the text will stay there for the entire week.

In the US there were some experiments on delivering high-volume content by broadcasting, say, a 30-second spot which flashed dozens or hundreds of images and you were supposed to record it on videotape and play it back frame-by-frame.

There was one local channel here which pointed a camera at a fishtank while idle; if you wanted a specific data package, you called a number to request it. I think the high-water mark for the concept was a few national ads where they said "we'll broadcast the entire Chevrolet catalogue at the top of the hour, have your VCR ready." The problem being, you had to run a second advertisement to get the audience ready for the first one!

Considering you're mentioning guilders - was this the thing shown on TV back then https://nos.nl/teletekst?

yes, on the national channels.

Original article author here: Yes, key pages were multiple times over teletext. It's a bit of a grey area for amateur radio regs, so I didn't mention it in the article, but you could use the software with say, an license-free part 15 short wave FM transmitter, to send an entire carousel of many pages. As such the code does have an option to flag ket pages and specify how many times they should be repeated over a carousel's broadcast.

I remembered my grand vision for teletext. All pages should be dedicated to a text based rpg using the Choose Your Own Adventure mechanic[0]

People want to fight orcs and goblins, ride dragons, cast magic missile and save the princess.

That (using teletext) one can update the plot dynamically makes for a fun creative challenge. Should probably draw a giant flow chart with the 999 states. When all pages are used you have to remove things before you can add things.

[0] - https://en.wikipedia.org/wiki/Choose_Your_Own_Adventure

ADHD brain just recalled that similar concept was used for traffic jams being sent along FM radio signal.

Not talking about stuff that would automatically change the FM station to the one with traffic announcements.

Our ~2012 Škoda Octavia had typical Volkswagen Audi Group navigation built in. It would receive data about traffic jams in the background, and incorporate it into route/navigation decisions.

Not sure if switch from FM to DAB carried that over too. Kind of doubtful since mobile phones took over navigation even before Android/iOS Auto stuff showed up.

Imagine a meshtastic network of devices across a city or country, broadcasting a set of rotating teletext pages with no ability to censor it. That would be something.

> with no ability to censor it Except, of course, policemen knocking on your door. Wouldn't be necessary anyways, most people would not even try broadcasting on the mere threat of arrest.

Seems like we have all the key technologies to edit anonymously and distribute info P2P-style with no known central control mechanism.

The same author dabbled in a similar project, so maybe there's a Teletext over ham radio tie-in possible?

https://spectrum.ieee.org/run-a-meshtastic-bbs

Author of the OP article here: Yes, you could 100% send teletext frames over meshtastic: if you're using the unlicensed bands you could even send full carousels with many pages, which is something that isn't really kosher under my reading of the FCC regs for amateur radio, which is why I stuck to a single page SSTV replacement in the article!

There are actually multiple implementation of networking over ham radio (though not using teletext).

Some of the limitations are that ham radio requires getting a license (it's easy, but it's a little bit of work and turns some people off), the user base is tiny (it's a niche inside a niche), it requires technical knowledge and specialized hardware, and legally it can't be encrypted or used for commercial purposes. That's okay if your plan is to broadcast messages without censorship, but not so great if you want to check email or browse https sites.

https://spectrum.ieee.org/build-a-longdistance-data-network-...

https://www.reddit.com/r/amateurradio/comments/5bj5w0/intern...

I can understand the appeal of that, but we live in a post-truth society where facts only matter to those who care about facts.

aprs is basically here

Considering how good LLMs are getting at building DSP code now, I expect to see a tidal wave of new digital modes start to pop up now. It's easy to conduct over the air tests on HF using the global kiwisdr receiver network and build agentic experiment, test, evaluate loops on simulated and real RF channels.

I recently learned that captions on BBC are teletext based (page 888) so I turned them on and got surprised that it's still working that way - especially considering I'm watching it basically via IPTV (using Dutch KPNs Android SmartTV app).

The 888 in the top right corner back in the day: https://youtu.be/rAk94cq23HQ?si=JLJMSqbUjKUsFcdQ just amazing that teletext was understood and ubiquitous to such an extent that just putting three numbers was important and clear enough to share in these very sparse idents.

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