Digital Telecommunication in HF band - WWWAN - World-Wide Wireless Area Network | Hacker News Reader

Digital Telecommunication in HF band - WWWAN - World-Wide Wireless Area Network

pretalx.sysmocom.de

65 pointspabs326 comments

How is this different from what the ham radio guys have? They were doing ip over ham in the 90s, i think, which is more performant than uucp for sure.

Not very different I think... on the air it's the same: they're using VARA, which has been introduced by a ham radio guy (https://rosmodem.wordpress.com/), and is widely used by ham radio operators.

I'm a bit annoyed by the closed and Windows-only nature of VARA (see also discussion https://old.reddit.com/r/amateurradio/comments/12d2s3e/would...), but well, it works well as far as I've heard.

Related but not quite the same: http://www.dxcluster.org/

Dxcluster used to use a lot of radio links to disseminate data. However fixed internet lines have become much cheaper, so there isn't the need to have massive HF antenna to create relay link any more.

> so there isn't the need to have massive HF antenna to create relay link any more.

HF is having quite a resurgance among various militaries.

I'm not sure why this was downvoted. The author is correct.

Given that space communications and the militarization of space is becoming more and more prevalent, we are on the cusp of seeing some military actions in space that could render a few defense agencies impotent with regards to C3.

"Multimedia"? Over HF where one "cell" (using the WWAN nomenclature) may have several tens kbps of total (uplink and/or downlink) throughput at most? (see Shannon-Hartley theorem, which is distinct from Shannon-Nyquist sampling theorem) But for emails and the rest of proposed use, sure.

Also, OsmoDevCon is iirc invite-only, making linking to its schedule on a public forum mostly pointless (visit #osmocom on Libera for more info; disclaimer: I wasn't invited, either). Unless, of course, a recording would be added (which it probably will), but it's not true yet (as the event didn't took place yet?)

If you consider SSB voice one medium, and CW morse code another, HF has been multimedia for more than a century :)

There's also SSTV. Surely images, voice and text counts as multi-media?

Uh, I didn't know SSTV had been used since the Apollo moon landings.

But what is it actually used for today? Or is it rather one of those we do, because we can?

Obviously they use this modem: https://github.com/Rhizomatica/mercury Any experience with it? How does it compare to VARA oder Pactor?

What HF means in this context? A few GHz? Also, for long range I thought the longer the wave length is, the better.

https://en.wikipedia.org/wiki/High_frequency

HF is 3 MHz to 30 MHz. Yes it does not make much sense, the term is ancient.

I mean, any higher and I’ll have to start thinking about printed circuit boards, shielded wires, and non-coat-hanger-based antennas…frankly if 30,000 kilocycles can’t get the job done, I’ll just have to light the thing on fire and use it to make smoke signals.

Best regards, 50 years ago

640 K[Hz] ought to be enough for anybody.

If you did a modicum of reading it makes sense.

Ancient? The HF band is still very much in use... Modern developments have not changed the fundamental properties of RF propagation. UHF ("a few GHz") can only be propagated in line of sight reliably. HF can literally travel around the world.

GP called the term ancient, not the band itself, and I find it hard to disagree with that.

Calling something “high”, “fast”, or “new” is rarely a naming decision that’ll stand the test of time, but given that there were already LF and MF below it, it did make sense at the time. Who could have predicted we’d go up all the way into visible light with our RF communications?

The only thing on a lower frequency used daily by most people would be contactless payment cards and maybe NFC at around 13 MHz.

Millimeter wavelength RF was already studied in the 19th century... The RF communication band you're talking about is smack dab in a band already defined in the original 1937 document.

Honestly the naming scheme makes sense to me. The spectrum is divided into 12 bands of equal (log) size, up to a frequency where we don't know whether such waves will ever be reliably generated at room temperature without breaking the laws of physics. Then these bands are consistently named from "extremely low" to "extremely high", with an extra annoying band at the top. Really, it could be worse.

I agree it could be worse but the idea it's really any good seems more like us being used to it than anything else. It's a stupid naming scheme. For a log scale I would really have been happier with everyone using band numbers or something rather than explaining "super high frequency" is higher than "Ultra high frequency" and, despite the terms, that's probably where most typical radio device use cases are these days.

Fortunately we have not just one but two competing band designators – IEEE (widely in use in e.g. satellite communication; L-band, Ku-band, Ka-band etc. come from that nomenclature) and EU/NATO (which seems somewhat obsolete) :)

In addition to that, hams (in study materials and exams) use wavelengths, which is always "fun" to convert from/to frequencies.

I'm not sure I understand. In 1937 we already knew that light and RF are both part of the EM spectrum so I don't know what you mean by generating waves that break the laws of physics (we have and had absolutely no issues generating waves with 100s of THz frequency). As a physicist coming from the optics I find naming in RF often quite puzzling, e.g. why do we call it microwave, while wavelengths are all longer that millimeters?

> we have and had absolutely no issues generating waves with 100s of THz frequency

In a way suitable for even medium range RF communication? No. That's what I mean. The required power would be insanely high. So high that it's not achievable without some breakthrough. I didn't literally mean "break the laws of physics", because that's something we obviously cannot do.

What do you mean? We routinely do satellite communications with free space optics, and fibre comms which at the backbone of all modern comms uses light around 193 THz.

UHF can be used with troposcatter techniques. Before satellites this was somewhat popular. It seems to be having a little bit of a comeback as well as you can get hundreds of miles of propagation fairly reliably and since it's higher frequency you can get a pretty wide bandwidth. Something that can fit on a small trailer can send hundreds of megabits hundreds of miles.

Even today, it still is higher than low and medium frequency :)

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