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Reviving Teletext for Ham Radio

spectrum.ieee.org

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Re: Reviving Teletext for Ham Radio

#11

Post by jlarocco »

joezydeco wrote: post #4

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.

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...

Re: Reviving Teletext for Ham Radio

#12

Post by BoxOfRain »

nickcw wrote: post #3

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…

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.

Re: Reviving Teletext for Ham Radio

#13

Post by joezydeco »

sucrosesucrose wrote: post #5
joezydeco wrote: post #4

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.

Re: Reviving Teletext for Ham Radio

#14

Post by mrkwse »

6510 wrote: post #10

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 as…

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.

Re: Reviving Teletext for Ham Radio

#15

Post by cf100clunk »

BoxOfRain wrote: post #12
nickcw wrote: post #3

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…

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.

Re: Reviving Teletext for Ham Radio

#16

Post by 1xn »

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.

Re: Reviving Teletext for Ham Radio

#17

Post by thcipriani »

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.

Re: Reviving Teletext for Ham Radio

#18

Post by reaperducer »

nickcw wrote: post #3

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…

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.

Re: Reviving Teletext for Ham Radio

#19

Post by reaperducer »

BoxOfRain wrote: post #12
nickcw wrote: post #3

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…

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.

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.

Re: Reviving Teletext for Ham Radio

#20

Post by golem14 »

1xn wrote: post #16

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.
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