Of course I was really only guessing at what percent errors were looked at for the lowest SNR...actually just going by some information published in conjunction with Patrick's and Pascal's mode information.
Perhaps one of the things that needs to be established IS how to determine the lowest SNR. I would think that for non-ARQ modes, it would be some percentage of the total possible throughput. However, to do this you need a standard text and not just a short line or two...you need a substantial paragraph with numbers and some special characters. Also, you would need to log the band and relative propagation conditions. All this to make any valid SNR statement. Walt/K5YFW -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] Behalf Of KV9U Sent: Thursday, February 22, 2007 1:41 PM To: [email protected] Subject: Re: [digitalradio] Re: DEX vs. MT-63 I was not aware that the lowest S/N ratios allow for significant error rates. For example, the British study had what seemed perfect data throughput when they listed the S/N ratio below noise, although under AWGN and that is more similar to VHF and up compared to HF. Based upon the multitone success of Pactor 3, it seems that having a moderate number of tones (18 perhaps?) might be better than having large numbers such as found with MT-63 (64 tones). What would happen with a DEX44 or DEX88, with or without FEC? 73, Rick, KV9U DuBose Walt Civ AETC CONS/LGCA wrote: >Rick, > >A couple of things to consider... > >Most of the published Lowest S/N (such as by Patrick, F6CTE, Pascal, F1ULT and >others is based on the signal level where you are getting about 2% errors. > >The lowest S/N for MT63 is - 8 dB for 5 bauds, - 5 dB for 10 bauds and -2 dB >for 20 bauds and is generally either error free or not decoding at all. > >DominoEX 16 is 15.625 baud ~100 WPM ~50 WPM w/FEC >DominoEX 22 is 21.533 baud ~140 WPM ~70 WPM w/FEC > >While no specific lowest S/N is given for DominoEX, I suspect that DominoEX 22 >is close to MT63-1K in throughput except that it more than likely DominoEx 22 >has a lower S/N than MT-63-1K. > >Therefore one would expect DominoEX-22 to work better than MT63-1K perhaps in >part due to the higher baud rate and less of a tendency to be affected by >Doppler. This might also be a reason that DominoEX 22 worked better than >DominoEX 16 w/FEC. > >As you say..."the ability to handle the vagaries of the ionosphere is often >more important than the raw ability to handle AWGN." > > > Announce your digital presence via our DX Cluster telnet://cluster.dynalias.org Our other groups: http://groups.yahoo.com/group/dxlist/ http://groups.yahoo.com/group/themixwgroup http://groups.yahoo.com/group/contesting http://groups.yahoo.com/group/wnyar http://groups.yahoo.com/group/Omnibus97 Yahoo! Groups - Join or create groups, clubs, forums & communities. Links
