The demodulator has it's own optimal filtering so the SSB rx filtering won't have any impact.
Flat tx filtering is a good idea, so that all carriers have equal power. - David On 21/01/15 23:01, Gullik Webjörn wrote: > Dear list, > > Currently the typical freedv / codec2 gear is a SSB transceiver and a > codec2/fdmdv modem. > Observing the signal on the waterfall, I can see that a fdmdv signal is > about half the bandwidth > of a SSB signal. Thus, I was thinking about changing the filter in the > transceiver, to gain an extra > dB or so by eliminating the difference in noise bandwidth. > > However, maybe this is NOT the way to go, maybe the signal processing in > the fdmdv modem is so > much superior due to cpu power, that THAT would be the area to focus on. > > We have discussed I/Q modulation/demodulation, and that even though this > is easily implemented, it > has not been done (but maybe tested??) yet. > > Is it your belief that a "dedicated" transceiver would significantly > improve codec2/freedv operation? > > Where is the biggest mismatch? Crystal filters ( passband shape / group > delay) , AGC, general amplitude/phase > in the signal chain (that is optimised for CW/SSB/RTTY)?? > > Gain / AGC ( passband mismatch)?? > > In short, how would a "near optimum" transceiver for this mode look > like, what can be eliminated, > what should be enhanced? > > Would a signal chain with independent carrier processing of the 16/17 > carriers gain anyting, I am here > thinking of individual carrier erasure due to multipath, or are we close > to optimal here? > > Your thoughts... > > Gullik / SM6FBD > > PS > Saw the video from linux-dev NZ, nice... > > > > ------------------------------------------------------------------------------ > New Year. New Location. New Benefits. New Data Center in Ashburn, VA. > GigeNET is offering a free month of service with a new server in Ashburn. > Choose from 2 high performing configs, both with 100TB of bandwidth. > Higher redundancy.Lower latency.Increased capacity.Completely compliant. > http://p.sf.net/sfu/gigenet > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > ------------------------------------------------------------------------------ New Year. New Location. New Benefits. New Data Center in Ashburn, VA. GigeNET is offering a free month of service with a new server in Ashburn. Choose from 2 high performing configs, both with 100TB of bandwidth. Higher redundancy.Lower latency.Increased capacity.Completely compliant. http://p.sf.net/sfu/gigenet _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
