--- In digitalradio@yahoogroups.com, "Vojtech Bubnik" <bubn...@...> wrote: > > > In a simple shoot out between olivia 250 x8 and msfk16 , olivia > > stopped decoding whilst mfsk was still at 100% ... thought that was > > not supposed to happen ? > > Hi Graham. > > I am certainly not surprised and it confirms my Gaussian noise tests. > Olivia trades sensitivity for automatic tuning. MFSK16's convolution > coding provides for high sensitivity, but does not give sharp enough > indicator, whether the data is valid. Basically the Hammond distance > of the code is too low to give reliable indicator. Olivia uses Welsh > block coding, which provides good data validity indicator, but has not > as high coding gain as convolution codes. > > For explanation of coding gain, see the excellent article from g3ruh > http://www.amsat.org/amsat/articles/g3ruh/105.html > > I believe the perfect weak signal mode for HAM radio is yet to be > designed with easy tuning of Olivia and high sensitivity of MFSK16, > combining both convolution and block codes. Maybe overlying MFSK16 > with Reed-Solomon block code and running multiple MFSK16 decoders with > half tone spacing will do the trick. > > 73, Vojtech OK1IAK >
The other thing was the initial test was mt63/500 ~ olivia 250 x 8 , MT dident do very well, so ended up with mfsk .. the single tone is handy as well , as many lf stns cannot handle linear modes like psk .. but with the stability of modern rigs I dont see why the original mfsk should not make a come back ? G ..
