Hi Glen Happy to comment, but there's quite a lot of material in your post below and I'm unclear on what you are trying to achieve.
Can you pls tell me what the goal of your proposed work is? Cheers, David On 5/7/20 6:43 pm, glen english wrote: > I've been looking at an coherent MSK modem for Codec2. I have not done > any coherent MSK modems since the late 90s. > > Using an SSB radio , at something like 1600 bps , there will still be > appreciable PAPR on MSK due to bandwidth constraint. probably about 3dB > PAPR on a 2400Hz wide radio. When bandwidth is constrained, the > constant envelope signal is no longer constant envelope... > > The is quite obvious using MSK441, the meteor scatter mode in WSJTX. It > operates at 2000 bps, and struggles a bit on bandwidth with most non-SDR > types . PAPR ends up around 4.5dB . Also the phase response of non flat > radios is usually aweful. A channel equaliser turned on to model and fix > your radio > > Now... > > OFDM doesnt need a specific radio equaliser, that's built in of course, > the uglyness of most radios can be obscured. . > > And if the only complication from the existing OFDM modem of David's is > the need to constrain PAPR, I think that perhaps constraining the PAPR > of David's existing modem , rather than a MSK modem from almost scratch > , might be more overall beneficial to everyone (HF as well) . I am > thinking an incompatible change to the existing modem to reduce PAPR to > something like 4.5dB might be the best of both worlds. yeah it might > cost a 0.5dB but oh well, you probably lose that now with PAPR > constraints. The existing 2FSK or 4FSK modem should also be brought up > to working. > > David, what are your candid thoughts ? > > glen. > > > On 6/23/2020 6:16 AM, David Rowe wrote: >> Hi Glen, > > > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
