Re: [digitalradio] Contestia 1K vs MT63?
Jose, Thanks for your comments and sorry I missed you yesterday. > I have doubts on this department. If the peak amplitudes are the same, > as may be happening with the audio tests, the decoding on those > conditions should be equally valid. The audio for each mode was normalized during the path simulation tests so I would assume the peak amplitudes were the same. > Vojtech points out that MT63 is more sensitive to distortions which are > pretty common with some not so careful operators. I'm glad Vojtech mentioned this. I think some may be overdriving their rigs unintentionally with MT63 by not taking the peak power ratio into account. > I did not find any details on my references, but seemingly interleaving > is done both in the time and frequency domains, so there is more chance > for MT63 to get the message thru, specially with long interleave. Certainly seems that way -- hard mode to beat when it comes to static crash resistance. Thanks for all Jose... Tony, K2MO - Original Message - From: "Jose A. Amador" <[EMAIL PROTECTED]> To: Sent: Saturday, October 11, 2008 7:43 PM Subject: Re: [digitalradio] Contestia 1K vs MT63? > Tony wrote: > >> Patrick, >> >> I get the same minimum SNR for Contestia but can squeeze -8db out of >> MT63 when using DM780 and IZ8BLY. > > Yesterday I had no luck with DM780 while monitoring Tony's QSO's on > 14106. Of course, I have not calibrated DM780, so that is no surprise. > Propagation was not good, but MultiPSK did fairly well. > >> 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. > > No doubt... > >> 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. > > I have doubts on this department. If the peak amplitudes are the same, > as may be happening with the audio tests, the decoding on those > conditions should be equally valid. Of course, Vojtech points out that > MT63 is more sensitive to distortions which are pretty common with some > not so careful operators. Fast attack slow decay ALC could have a chance > of correcting some of the overloads after the transmit IF, but the rest > of the chain, from the audio input to the IF should receive proper audio > levels. I have seen rebel cases of distorted PSK-31 when people closes > the mic gain and distortion remains... because the early stages of the > transceiver are already overloaded, and I had a real bad luck when > explaining that to the other operator. People should know their way > around... > >> 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 was browsing my references this afternoon (local) and I I decided not > to send a reply, since it seemed that Vojtech had a good point and was > not worth arguing about it. Nevertheless, I wonder how the degradating > effect of -30 to -20 dB IMD, the usually accepted values when adding > that to the channel noise. > > Even more when I read that Contestia was devised with a flat envelope on > mind (nonlinearity does not affect it) and uses about the same > Walsh-Hadamard code. > > But it _might_ mean, conversely, that Contestia is more power greedy, an > important consideration for emergency operation. > >> 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? > > I did not find any details on my references, but seemingly interleaving > is done both in the time and frequency domains, so there is more chance > for MT63 to get the message thru, specially with long interleave. On the > other hand, if someone "pulls the carpet" (heavy doppler) there is a > risk that MT63 will fail strepitously with bits falling on the wrong > bins while a mode with less, wider frequency "bins" (like Contestia or > Olivia) will really shine. > > I had really a low esteem for MT-63, but it had been hard to make a > MT-63 QSO before Tony started the present tests campaign. It just > happens that each mode should be used according to its most promiment > strengths. > > I still have low steem for Chip-64... 8-) > > 73, > > Jose, CO2JA > > > > >
Re: [digitalradio] Contestia 1K vs MT63?
Tony wrote: > Patrick, > > I get the same minimum SNR for Contestia but can squeeze -8db out of > MT63 when using DM780 and IZ8BLY. Yesterday I had no luck with DM780 while monitoring Tony's QSO's on 14106. Of course, I have not calibrated DM780, so that is no surprise. Propagation was not good, but MultiPSK did fairly well. > 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. No doubt... > 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. I have doubts on this department. If the peak amplitudes are the same, as may be happening with the audio tests, the decoding on those conditions should be equally valid. Of course, Vojtech points out that MT63 is more sensitive to distortions which are pretty common with some not so careful operators. Fast attack slow decay ALC could have a chance of correcting some of the overloads after the transmit IF, but the rest of the chain, from the audio input to the IF should receive proper audio levels. I have seen rebel cases of distorted PSK-31 when people closes the mic gain and distortion remains... because the early stages of the transceiver are already overloaded, and I had a real bad luck when explaining that to the other operator. People should know their way around... > 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 was browsing my references this afternoon (local) and I I decided not to send a reply, since it seemed that Vojtech had a good point and was not worth arguing about it. Nevertheless, I wonder how the degradating effect of -30 to -20 dB IMD, the usually accepted values when adding that to the channel noise. Even more when I read that Contestia was devised with a flat envelope on mind (nonlinearity does not affect it) and uses about the same Walsh-Hadamard code. But it _might_ mean, conversely, that Contestia is more power greedy, an important consideration for emergency operation. > 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? I did not find any details on my references, but seemingly interleaving is done both in the time and frequency domains, so there is more chance for MT63 to get the message thru, specially with long interleave. On the other hand, if someone "pulls the carpet" (heavy doppler) there is a risk that MT63 will fail strepitously with bits falling on the wrong bins while a mode with less, wider frequency "bins" (like Contestia or Olivia) will really shine. I had really a low esteem for MT-63, but it had been hard to make a MT-63 QSO before Tony started the present tests campaign. It just happens that each mode should be used according to its most promiment strengths. I still have low steem for Chip-64... 8-) 73, Jose, CO2JA
Re: [digitalradio] Contestia 1K vs MT63?
TKS Tony for the information, >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'. Yes MT63 has a good frequency and time diversity. And at 100 wpm, there are no many modes... A Contestia 32 / 1K could be a better alternative than the 16/1K. 73 Patrick - Original Message - From: Tony To: digitalradio@yahoogroups.com Sent: Saturday, October 11, 2008 8:40 PM Subject: Re: [digitalradio] Contestia 1K vs MT63? 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: 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* > >
Re: [digitalradio] Contestia 1K vs MT63?
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: 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* > >
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*
