Hello Rick and all, One information about the S/N ratios on Multipsk. Normally, it is accepted 2 % of errors (because perfection would need a relatively higher S/N). However, it is theoritical: as for example, in QRSS (slow CW) it is not possible to appreciate 2 % of errors, except after hours, so in that case it is a bit subjective...
The test is done with gaussian noise only and normalized to 3 KHz of noise. ARQ FAE: It would be difficult to appreciate as it is a ARQ mode with a memory. In general, in case of very low S/N, with two (or three) failed received frames, the right frame can be obtained through the mean value of the failed frames. Due to the ARQ memory, the limitation in ARQ FAE is clearly not on the message quality but on the detection of the frame. 73 Patrick ----- Original Message ----- From: "Rick W." <[EMAIL PROTECTED]> To: <digitalradio@yahoogroups.com> Sent: Saturday, July 12, 2008 3:40 PM Subject: Re: [digitalradio] Re: KV9U - Mode Sensitivity / Robustness > What Tony has done is quite helpful to many of us and I printed out his > message as a reference. For some time I developed a chart of many of the > parameters of the different sound card modes to get some idea of what > modulation they are using, baud rates, throughput, ITU Emission > Description (if I can figure it out), bandwidth, minimum S/N ratio, etc. > > There are quite a few tradeoffs with bandwidth, throughput speed, size > of ASCII character set, robustness, weak signal capability. Those of us > who have used digital modes for many decades have at least a "feel" for > what is working the best under given conditions. But even then I have > overlooked some modes that other groups have found useful for say, high > QRN conditions (CHIP 64). > > When a new mode comes out we typically have a lot of testing for a few > of us who have interest in this, but after a few weeks or months, this > tends to subside as we make a value judgment on whether a new mode has > certain new features or benefits over the older ones. > > Your results confirm what has worked out in practice for me. For non-ARQ > modes, MFSK16 seems to be the narrowest mode available that can work the > deepest into the noise on a consistent basis and with the highest > possible throughput speed. It may not be as robust against certain kinds > of interference since it is narrow. It also requires exact tuning and > stability. > > Olivia 500/16 is the second choice but extremely slow at ~20 wpm. In > some cases it might be better than MFSK16 with certain kinds of > interference? And it is less critical to tune. > > One thing that may need more comparison is between Olivia and DominoEX > 4. Consider that even the slow 4 baud Domino mode is faster (27 wpm) > than Olivia 500/16. It was developed to handle extreme multipath > conditions, such as could be found on the lower HF bands, but because of > the slow baud rate, wouldn't it also be susceptible to doppler? This > could also be an issue between Olivia which has much faster baud rates > than MFSK16? > > Most of your numbers match up quite closely to Patrick, F6CTE's tests > that he shows in the help files of Multipsk. I use those numbers as the > main ones for comparison. The exception that stands out (excluding Hell > which is more subjective), is your DominoEX11 since he lists it as much > more sensitive. Curiously, when I have tested DominoEX11 against other > modes, it just did not seem to perform as well as one would expect if it > was a -12 dB S/N mode. But your -8 dB numbers might explain why that is > the case. > > Have you considered testing the FAE400 mode? This mode should be > competitive with most of the modes but is an error free ARQ mode. At > this time it seems to clearly be the very best sound card ARQ mode for > difficult conditions. It will stop throughput at signal > levels/conditions where you might be able to use MFSK16 or Olivia > 500/16, but with even a modest signal the speed is much faster (varies > from 60 to over 100 wpm depending upon block size) than any of the other > modes for the bandwidth. > > Another point well taken is that the best modes for weak signal are the > narrow ones, typically under 500 Hz. > > 73, > > Rick, KV9U > > > > > Tony wrote: >> Rick, >> >> >Has anyone compared Domino EX with the top modes that get >> >through the worst conditions and, if so, what have you found? >> >> I've compared a variety of sound card modes for sensitivity and >> robustness using an HF path simulator (see below). >> >> I first tested each mode for sensitivity by finding the lowest >> signal-to-noise ratio that would still produce 100% decode. These were >> direct-path simulations with no ionospheric disturbance. >> >> >> For what it's worth, DominoEX 11 baud, had about the same sensitivity >> as MT63 and Olivia 500/4. DominoEX 4 baud had about the same >> sensitivity as MFSK16. >> >> Olivia 500/16/8 were more sensitive than DominioEX 11 as well; Olivia >> mode sensitivity would increases with an increase in the number of tones. >> >> Things got interesting while testing for robustness with the >> ionospheric simulator. The Domino EX modes fell short to the point >> where they would not decode at all with certain disturbances >> regardless of SNR. >> >> The DominoEX modes seemed sensitive to frequency spread found on >> the more disturbed ionospheric paths, especially polar and >> low-latitude paths. >> >> I think it's important to remember that these are simulations and >> on-air testing may show different results. There are no static crash >> simulators with Pathsim so it's hard to simulate things like >> mode recovery time etc. >> >> If anyone is interested in path simulation, it's important to >> normalize the audio before it's feed into the simulator. Normalizing >> keeps the audio at the same level so one mode is not any louder or >> weaker than another. >> >> Tony, K2MO >> Kings Park, NY >> >> ______________________________________________________ >> >> >> *Sensitivity Test ( lowest SNR that will produce 100% decode)* >> (DIRECT PATH - NO IONOSPHERIC DISTURBANCE) >> >> RTTY 45................... -5db >> Feld Hell.....................-6db* >> DominoEX-11........ -8db >> MT63 1K................. -8db >> Olivia 500/4.............. -8db >> Olivia 500/8..............-10db >> PSK31................... -10db >> Olivia 500/16 .......... -12db >> MFSK16....................-14db >> DominoEX-4 baud...-15db >> >> * Simulated quiet band condx. Good contrast between text and white >> background. >> >> >> ______________________________________________ >> >> *Sensitivity Test SNR -12db * >> (DIRECT PATH - NO IONOSPHERIC DISTURBANCE) >> >> MFSK16.....................Perfect Copy >> Olivia 500/16..............Perfect Copy >> DominoEX 4 baud....Perfect Copy >> Oivia 500/8..................90% >> Olivia 500/4.................90% >> DominoEX 11 baud...90% >> PSK31.........................90% >> Feld Hell......................Faint Text * >> MT63 1K.....................No Copy >> RTTY 45 baud............No Copy >> >> * Feld Hell somewhat readable at this SNR under extremely quiet condx. >> >> _______________________________________________________ >> ** >> *Sensitivity Test **SNR -15db* (faint signal in waterfall) >> >> (DIRECT PATH - NO IONOSPHERIC DISTURBANCE) >> >> DominoEX 4bd..........100% Copy >> MFSK16.......................95% Copy >> Olivia 1K/32.................90% Copy >> Olivia 500/16...............90% Copy >> >> >> *Olivia 500/8................. <50%* >> *THE QUICK BROWN FOX :UMPS OB$[T,3AZY DOG >> T.`8 dIC `"N FSX JUd VCR g&?GZY 1PaOlj/== BROWZ+_* >> */|mu_S R pHB\7JY 9OG* >> ** >> Olivia 500/4...................No Copy >> >> >> *DominoEX 11bd...............50%* >> *tTHE QUICK BDOWN FOXGUMPSLiVER IE LA ' Y BCI* >> *THQUICK) ROWN FOX JU S OVCu THE LAZY DOG* >> *TH QUo OWN FN0 ZUMLx OGR THE tZY DOa? L* >> >> *PSK31...........................<50%* >> E QUIhK BRO FOs J.MPS OVEC THE s >> -t( a OGTr �ITBRO N Ft uJU0PbtaVEXE LAZY t >> OpHE uPIOK BROWN FtoMPS OT0R li0 LA rY Ctep >> >> MT63..........................No Copy >> Feld Hell.....................No Copy >> RTTY 45....................No Copy >> >> _______________________________________________________________ >> >> >> *_High-_**_Latitude Path Simulation_* >> ** >> *(Moderate High-**Latitude Disturbance,* *3ms path delay, 10hz >> frequency** spread, SNR -8db)* >> ** >> *(3ms path delay, 10hz frequency spread, SNR -8db)* >> >> MFSK16......................Perfect Copy >> Olivia 500/16...............Perfect Copy >> Olivia 500/8..................Perfect Copy >> Olivia 500/4..................90% >> Feld Hell........................90%* >> DominoEX 4bd..........No Copy >> DominoEX 11bd........No Copy >> PSK31.........................No Copy >> RTTY45........................No Copy >> MT63............................No Copy >> >> * Text to background contrast marginal but readable. >> >> _______________________________________________________ >> >> >> *_Mid-_**_Latitude Path Simulation_* >> ** >> *_(_Storm condition **Mid-Latitude Disturbance,* *2ms path delay, 1hz >> frequency spread, SNR -8db)* >> ** >> MFSK16......................Perfect Copy >> Olivia 500/16...............Perfect Copy >> Olivia 500/8..................90% >> Olivia 500/4..................90% >> DominoEX 4bd............90% >> MT63 1K.......................90% >> Feld Hell........................<90%* >> >> *Good text contrast, missing characters >> >> *DominoEX 11bd* >> THE QUIRK BROWN FOX JUMPTYOFttT3G LAZY DOG >> THE QROWN FOiRJUMPtJeoER TLAZY DOG >> THE QUICK NNOWOXlrUMPS OVER ti8AZY DOG >> >> *PSK31* >> THe EaoICK BROWN F Jto c OTeR THE LAZY DOG >> THE Q4Icš BROWN MOX p HMPS OVIRHE LAZY DOG >> Tr4 QUICK BROWNa o e o JUMPS r -ER THE LY >> >> *RTTY45* >> XMXSPYUIVK BRGWN FOKGDUMHR KZ4 ZILAZYHDOG >> OVZHE QUFKH?492,6FF JINQ QOCSKQ0/6&)'6 BMXDQ >> NQ QUICK YBRTZNLFMY JUVHS OVER PHE )-+6 DOG >> >> ______________________________________________________________ >> >> *_Low-_**_Latitude Path Simulation_* >> ** >> *_(Storm condition Low-Latitude Disturbance, 6ms path delay, 10hz >> frequency spread, SNR -8db)_* >> ** >> MFSK16...................Pefect Copy >> Olivia 500/16............Perfect Copy >> Olivia 500/8..............90% >> Olivia 500/4..............90% >> Feld Hell....................Poor Copy* >> DominoEX 4bd .......No Copy >> DominoEX 11bd......No Copy >> MT63 1k....................No Copy >> PSK31......................No Copy >> RTTY45.....................No Copy >> >> * Feld Hell letters were diffuse (spread) making it difficult to read. >> >> >> >> >> No virus found in this incoming message. >> Checked by AVG - http://www.avg.com >> Version: 8.0.138 / Virus Database: 270.4.8/1547 - Release Date: 7/11/2008 >> 6:05 PM >> > > > ------------------------------------ > > Announce your digital presence via our Interactive Sked Page at > http://www.obriensweb.com/sked > > Check our other Yahoo Groups.... > http://groups.yahoo.com/group/dxlist/ > http://groups.yahoo.com/group/contesting > http://groups.yahoo.com/group/themixwgroup > Yahoo! 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