4 ms·

Out of curiosity, has anyone implemented a dial-up modem with GNU Radio? Or if not, what would need to be implemented, V.92?

Zenst 7y ago
I found this from 2010, that uses GNU radio piped into a soft modem: http://oz9aec.net/radios/gnu-radio/connecting-gnu-radio-to-the-multimon-software-modem http://oz9aec.net/radios/gnu-radio/connecting-gnu-radio-to-t... Which would be the easiest way, unsure if you could do it purly in GNU Radio as not that up upon it, though software modems been around for a while, and more optimised code for the task. Historically the earliest software modems date back to the 90's.
abbeyj 7y ago
Not using GNU Radio but perhaps you might be interested in http://www.whence.com/minimodem/ http://www.whence.com/minimodem/. It only supports really old standards, up to 1200bps. But later modems should, in theory, be backward compatible so if you don't care about speed this could possibly work.
rasz 7y ago
http://www.whence.com/minimodem/ http://www.whence.com/minimodem/ does bell 103 https://www.youtube.com/watch?v=1Pmxkt9mYgM https://www.youtube.com/watch?v=1Pmxkt9mYgM This dude https://www-users.cs.york.ac.uk/~fisher/modem/ https://www-users.cs.york.ac.uk/~fisher/modem/ wrote V.32 soft modem stack for SGI Indy back in 1996 I remember reading back in the day in hacker zines about magic police modem tapping boxes, but no idea how would that work in the age of echo cancellation.
- therealx 7y ago
  You'd need to get the secret info on the frequency hopping scheme as well as the shared encryption key. I've heard of units being ripped out of police cars for this reason.
  - rasz 7y ago
    I meant dialup modem tapping. 2600 or phrack had something about feds being able to wire into telephone line and record/live decode modem connection. You could easily write something like this in GNU Radio for <=2400 links (or use minimodem), but anything higher transmits full duplex on same frequencies - both modems mutually jam each other.

Zenst 7y ago

I found this from 2010, that uses GNU radio piped into a soft modem: http://oz9aec.net/radios/gnu-radio/connecting-gnu-radio-to-the-multimon-software-modem http://oz9aec.net/radios/gnu-radio/connecting-gnu-radio-to-t... Which would be the easiest way, unsure if you could do it purly in GNU Radio as not that up upon it, though software modems been around for a while, and more optimised code for the task. Historically the earliest software modems date back to the 90's.

abbeyj 7y ago

Not using GNU Radio but perhaps you might be interested in http://www.whence.com/minimodem/ http://www.whence.com/minimodem/. It only supports really old standards, up to 1200bps. But later modems should, in theory, be backward compatible so if you don't care about speed this could possibly work.

rasz 7y ago

http://www.whence.com/minimodem/ http://www.whence.com/minimodem/ does bell 103 https://www.youtube.com/watch?v=1Pmxkt9mYgM https://www.youtube.com/watch?v=1Pmxkt9mYgM This dude https://www-users.cs.york.ac.uk/~fisher/modem/ https://www-users.cs.york.ac.uk/~fisher/modem/ wrote V.32 soft modem stack for SGI Indy back in 1996 I remember reading back in the day in hacker zines about magic police modem tapping boxes, but no idea how would that work in the age of echo cancellation.

therealx 7y ago
You'd need to get the secret info on the frequency hopping scheme as well as the shared encryption key. I've heard of units being ripped out of police cars for this reason.
- rasz 7y ago
  I meant dialup modem tapping. 2600 or phrack had something about feds being able to wire into telephone line and record/live decode modem connection. You could easily write something like this in GNU Radio for <=2400 links (or use minimodem), but anything higher transmits full duplex on same frequencies - both modems mutually jam each other.