Patrick, I get the same minimum SNR for Contestia but can squeeze -8db out of MT63 when using DM780 and IZ8BLY. Some MT63 programs have a higher decode threshold for reasons you've mentioned previously.
The threshold difference shows on-air as well as under controlled conditions and so it would seem that the best way to get the most out of MT63 is to use software that decodes deeper into the noise. The 10-to-1 peak-to-average power ratio is an excellent point and it's obvious that Contestia will put more RF into the air on average. There's no doubt in my mind that the Contestia 16-1K will do better most of the time. On the other hand, it does not seem to recover from the complete drop-outs that occur during deep fading or with lightning static the way MT63 does. I've tested this theory by removing short 1-to-3 second segments of the signal at random intervals and the mode continues to print despite the missing 'chunks'. As you say, this could be due to the difference in modulation speeds. Is there an alternative mode that I can test that might have similar characteristics? Thanks, Tony, K2MO ----- Original Message ----- From: "Patrick Lindecker" <[EMAIL PROTECTED]> To: <digitalradio@yahoogroups.com> Sent: Saturday, October 11, 2008 5:02 AM Subject: Re: [digitalradio] Contestia 1K vs MT63? > Hello Tony, > > According to my measures (under noise only): > * "16-1K": "Fast" 16 tones, bandwidth=1000 Hz, speed=62.5 bauds, 78.2 wpm, > lowest S/N =-9 dB, > > * MT63 1K: 100 wpm, lowest S/N - 5 dB for 10 bauds (perhaps -7dB with the > original program) but due to the > Pmean/Ppeak: 0.1, it is only theoritical, except if you prefer QRP > transmissions. > >>I'm not sure if that's an accurate assessment as to why there is a >>difference, but it would seem so. Wonder if anyone can shed some light on >>this. > The difference in Selective Fading conditions is perhaps due to the > modulation speeds which are rather different. > 73 > Patrick > > ----- Original Message ----- > From: Tony > To: digitalradio@yahoogroups.com > Sent: Saturday, October 11, 2008 7:44 AM > Subject: [digitalradio] Contestia 1K vs MT63? > > > All, > > I was playing with the Contestia mode in an attempt to duplicate the wpm > rate of MT63. I configured Contestia with 16 tones and a bandwidth of 1K. The > sensitivity of the two seemed to be the same and the wpm rate appeared to be > close. > > I then tested both modes with the HF path simulator dialed-in for selective > fading with the SNR set a few db above the minimum decode threshold. As you > can see below, print was better with MT63. > > The deep fades caused garbled characters with Contestia and it would appear > the better copy with MT63 is a result of the redundancy built into the mode. > > I'm not sure if that's an accurate assessment as to why there is a > difference, but it would seem so. Wonder if anyone can shed some light on > this. > > Tony, K2MO > > > Path Simulation : Selective Fading > SNR : -3db / -6db > > > Contestia 1K / 16 tone > > SNR -3db > > THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG > THE QUICK BROWN FOS OVER TH- >G > THE BROWN FOXMPS OVER THE LAZY DOG > THE QUICRO,N FOX JUMPS OVELAZY DOG > > SNR -6db > > TE QUCK BROW FOX JUMPS OVER THE LAZY DOG > THE QUG2NOWNS YVER THOEG > THE BROWN FO#UBR OVER TE LAZY DOG > THE QUIC^_^N FOX JUMPS OVELAZY DOG > > > MT63 1K > > SNR -3db > > *DE K2MO* > THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG > THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG > THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG > THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG > *EOT* > > SNR -6db > > *DE K2M > TH QUICK &AOWN FOX JUOP; OVrR THE LAZY ROG > THE Q%ICK BROWN FOX JUMPS OVER THE LAZY DOG > THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG > THE QUICK BROWNFOX JUMPS OVER THE LAZY DOG > *EOT* > >
