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Baud rate replaced by bandwidth limit (www.radioworld.com)

submitted 10 months ago by [email protected] to c/[email protected]

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Bands with a 300 baud rate limitation eliminated by this order are the 160 meter band; 80 meter band; 40 meter band segments 7.000–7.100 MHz and 7.100–7.125 MHz; 30 meter band; 20 meter band segment 14.00–14.15 MHz; 17 meter band segment 18.068–18.110 MHz; 15 meter band segment 21.0–21.2 MHz; and 12 meter band segment 24.89–24.93 MHz. The 10 meter band segment 28.0–28.3 MHz has a 1200 baud rate limitation, which is also lifted.

“Instead, the commission establishes a 2.8 kHz bandwidth limitation in the applicable amateur radio bands,” it said.

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[–] [email protected] 3 points 10 months ago

I'm excited to see the new digital modes people bring to ham radio, or invent.

[–] [email protected] 2 points 10 months ago (1 children)

I kind of like this. As a younger ham, I'm more used to thinking of digital transmissions in terms of bitrate (i.e. my Ethernet network is 1 Mbps) and using baud in amateur radio almost feels like an anachronism.

[–] [email protected] 1 points 10 months ago

On HF, unfortunately, physics is going to keep you from having high speed data. The Shannon–Hartley theorem puts a ceiling on the maximum bitrate of a channel in the presence of noise. If you are on HF with your 100w transceiver and a dipole antenna, your signals are always going to be weak enough on the other end of a skywave contact to limit your data throughput. Even given a magical ham prodigy that invents the best mode imaginable, it's going to be Kbps, not Mbps. If you want to learn about the development of open source, higher throughput digital modes for HF, I highly recommend David Rowe's blog on the development of FreeDV over the years. There's even a recent move to general data in addition to digital voice. However, we are talking about single digit Kbps digital. There are some other modems used by the Winlink folk that are a little higher. The drop of the baudrate limit will just remove an artificial contraint, and headache, on that development.

On line-of-sight VHF and up connections, it gets easier and easier as you have higher gain antennas pointed at each other and lower natural noise figures.

[–] [email protected] 1 points 10 months ago (1 children)

personally, I think the limit should’ve been higher, at least 5 kHz, when the AM Phone guys are occupying 10 to 15 kHz with their hi-fi broadcast set ups.

And a hard bandwidth limit really does limit total data rate, the symbol rate limit didn’t - exactly the opposite effect that the loud anti-baudrate-limit people wanted

[–] [email protected] 1 points 10 months ago

Bandwidth doesn't put a hard limit on bitrate either. It's one variable, but there's also SNR (See Shannon). With a fixed bandwidth, you can have low bitrate and excellent low-SNR performance (think of Olivia), or you can have higher bitrates, and require stronger signals. For practical purposes though, you are not going to get highspeed internet on HF. But that's what sharing is like. 🤷‍♂️