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." 73, Walt/K5YFW -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] Behalf Of KV9U Sent: Thursday, February 22, 2007 12:34 PM To: [email protected] Subject: Re: [digitalradio] Re: DEX vs. MT-63 I did not see any response to this but each of the DominoEX modes does have an estimated SNR For example: DEX4 = -14.5 dB DEX5 = -14 DEX8 = -13.5 DEX11 = -12 DEX16 = -10.5 DEX22 = -9 Add about one 1 db better SNR for using the FEC mode. It does seem that DEX22/FEC works better than DEX11 without FEC in many cases even though the throughput speed is about the same. However, under weak signal condx, I suspect that DEX11 wihout FEC would work deeper into the noise. As I am finding out on many HF circuits, the ability to handle the vagaries of the ionosphere is often more important than the raw ability to handle AWGN. I did think that MT-63 would do better than DEX11/FEC and DEX22/FEC, but it was much worse during the 160 meter test. Signal strengths were generally quite good though and QRN was not too bad considering the time of year here in the northern hemisphere. It will be most interesting to see what happens this summer with static crashes. It just seemed like DEX was able to handle static crashes better than other non-ARQ modes. 73, Rick, KV9U DuBose Walt Civ AETC CONS/LGCA wrote: > Coding Coding >Mode Baud Speed Correction Convolution Interleaving SNR >(in dB) Bandwidth >DominoEx11 10.766 77 WPM No No Not Stated >Not Stated 194 Hz >DominoEx22 21.533 154 WPM No No Not Stated >Not Stated 388 Hz >MT63-1K 10 100 WPM No No Yes > -5 1000 Hz > >Perhaps the bandwidth of MT63 and its SNR threshold may have been the >difference. But I don't know what the SNR threshold of DEx11 and DEx22 are. >Also, they are different types of modulations. > >Walt/K5YFW > > > > 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
