Rick, > The reason that I use various modes is to discover those that work the > best for most conditions on a given band and maintain a reasonable > throughput
I agree. Knowing which modes perform well when conditions deteriorate is helpful. I complied the digital mode HF simulations for that reason. >The MT-63 mode seems well suited for moderate speed (50 to 200 wpm) > under conditions with periodic interference where a part of the data is > obliterated The 1K mode does seem to recover well from lightning static and prints well when QRM'd. It doesn't seem to mind when other MT63 signals overlap by 25% or so either. That's something most digital modes can't do. > It needs a much stronger signal than some other modes in order to do this by > perhaps 5 to 10 dB The simulator says that MT63 has a minimum SNR of -8db for 100% throughput. That's about 2db less than PSK31 and about 6db less than MFSK16. If you place an RTTY signal over the top of MFSK16 or PSK31 signals, they will stop printing. MT63 will keep going. Of course, it's a much wider mode and has lots of redundancy. > isn't it fair to say that MFSK16 is about the best choice for robustness, > bandwidth, and speed for keyboarding? I think it is a well balanced mode. I also think it's hard to beat multi-tone FSK modes for robustness. They are much less susceptible to the effects of ionospheric Doppler and multi-path than other modes. They were the only mode types that withstood the 30Hz frequency spread during the high-latitude tests. That's about as brutal as it gets. > Or do you find that with stronger signals, the slow version (50 Hz/50 > wpm) of MT-63 gets through lightning static and QRM better than even the > new MFSK versions designed into the fldigi program? Is there a way to > simulate this with the software tests? I've tried to simulate lightning static by mixing real QRN with digital mode audio, but it did not work out well. I think a better approach might be to remove short segments of signal to simulate the type of heavy static crashes that would obliterate the signal entirely. It's still missing the AGC capture effect, but it should tell something about mode recovery after a drop-out. Tony, K2MO Simulation: High Latitude DisturbedPath delay: 7msFrequency spread: 30Hz SNR: -3db (weak signal)Mode ThroughputContestia 500/16.................100% CW 20 WPM........................100% Olivia 500/16....................100% Olivia 500/8.....................100% Olivia 500/4......................95% RTTYM**...........................95% MFSK31........................... 90% MFSK16............................75% RTTY..............................40%Chip-64...........................10% Chip-128**....................no copyDominoEX-4....................no copy FEC-31........................no copyJason Turbo (Fa...............no copyMT631K........................no copyPSK10.........................no copy PSKAM10.......................no copyPSK31.........................no copy PSK63.........................no copyThor-11.......................no copy ThrobX-4......................no copy Feld Hell....................Readable ----- Original Message ----- From: "Rick W" <[EMAIL PROTECTED]> To: <digitalradio@yahoogroups.com> Sent: Saturday, September 13, 2008 9:33 AM Subject: Re: [digitalradio] MT63 freq ? > The reason that I use various modes is to discover those that work the > best for most conditions on a given band and maintain a reasonable > throughput for a specific use. The MT-63 mode seems well suited for > moderate speed (50 to 200 wpm) under conditions with periodic > interference where a part of the data is obliterated, but enough gets > through for solid printing. It needs a much stronger signal than some > other modes in order to do this by perhaps 5 to 10 dB and to get the > higher speed (200 wpm) it needs a much wider footprint (2000 Hz) than > most other digital modes. Tuning can be difficult as signals get weaker > because the waterfall pattern starts to look like background noise. > > For casual QSO use, it seems to me that a speed of around 40 wpm, which > is a common speed for the narrow (PSK31) and relatively narrow (MFSK16) > modes works well for most hams. When conditions get more difficult, as > long as the signals are not too weak, some of the Olivia modes may be > the best choice if you can tolerate the slower throughput. > > Based on K2MO's tests and other hams practical on air experience, isn't > it fair to say that MFSK16 is about the best choice for robustness, > bandwidth, and speed for keyboarding? When conditions allow there are > now a number of additional MFSK baud rates, such as used with NBEMS. The > main difficulty is accurate tuning, but MFSK does have a mark position > during idle, that you can line your cursor with to get close to the lock > in frequency. > > Or do you find that with stronger signals, the slow version (50 Hz/50 > wpm) of MT-63 gets through lightning static and QRM better than even the > new MFSK versions designed into the fldigi program? Is there a way to > simulate this with the software tests? > > 73, > > Rick, KV9U >
