> 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
