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by TheRealEdAbbey 3240 days ago
Yep, PSK31 has a baud rate of 31.25 - that's literally 31 bits per second. There's no practical use for that in modern commercial or consumer applications.

In amateur bands, symbol rate below 28 MHz is limited to 300 baud.
1 comments
vvanders 3240 days ago
And anything in the 2M band is also symbol rate limited(I want to say it was 1200baud but I could be wrong).

It's really frustrating if you want to do any development with digital modes.

[edit]

Looked it up, it's a 19.6k symbol rate limit(rather than leave it open and restrict bandwidth). You can carry a ton of data on 2M if you wanted but legally you can't exceed the speed of an old dial up modem.

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lb1lf 3240 days ago
Are US ham bands really symbol rate (rather than bandwidth)limited?

Here in LA (Norway, for the ham prefix challenged), we can modulate in whatever way we feel like on 2M, as long as the signal bandwidth does not exceed 18kHz.

(So, using a clever modulation scheme, you could get very close to the Shannon limit for the given channel bandwidth and noise level - assuming a very healthy 30dB S/N, one should be able to wring approx. 180kbps from an 18kHz channel. (Granted, in the real world with filters without infinitely steep skirts we'd get nowhere near this - but, let's say you could get 1/3 or so without trying too hard.)

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vvanders 3240 days ago
It's actually both, 20Khz bandwidth and the 19.6k symbol rate.

I love amateur radio but at least on the 2m bands it's mostly dominated by people just chatting on repeaters with others they already know or dead quiet. I monitor 146.52(our calling frequence) on my ~300mi weekly trip and I've made only one contact in 2 years.

APRS is pretty dead, there's a ton of interesting stuff that could be done on the ECC and symbol rate front but no one really seems interested. Not much has changed on the spec for a long time. Compared to some other countries where they have some very robust and flourishing 2m digital modes it's a shame.

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TheRealEdAbbey 3240 days ago
Essentially, yes. My guess is that it's due to the fact that amateur radio for a long time has been CW and SSB, where there isn't much bandwidth issue. Digital modes are the new kid on the block (especially considering the average age of US hams is probably quite high), so rather than addressing the root issue, they decided just to target that new kid.

There are bandwidth restrictions on the 60m band, where amateur radio is secondary.

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