[Gah, keep forgetting to switch the From: address] Hi, On 13/04/13 08:44, Kristoff Bonne wrote: > On 12-04-13 20:04, Bruce Perens wrote: >>> >> The low-pass filter should be passing everything below about 22.05 or >>> >> 24 kHz, right? Even an imperfect filter should be fine. >> > Oh. Kristoff, is the modem not using Manchester encoding? > No, I might be wrong but I guess this would double the required baudrate. > > The 4800 bps modem is simply 4800 baud at 1 bit/symbol. For Manchester > encoding, you would needs 2 bits per symbol.
This might be an absurd suggestion, I don't know... but would the 1600bps Codec2 scheme work? This has the side-effect of being directly compatible with HF FreeDV; the bit-stream merely needs re-modulation and framing as the actual audio data is the same, making HF-to-VHF/UHF gateways trivial. Manchester encoding would mean an effective rate of 2400; which would still allow for 800 bits of headroom for things like synchronisation and ID headers, etc. -- Stuart Longland (aka Redhatter, VK4MSL) I haven't lost my mind... ...it's backed up on a tape somewhere. -- Stuart Longland (aka Redhatter, VK4MSL) I haven't lost my mind... ...it's backed up on a tape somewhere. ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
