All, Added several modes to the path simulation tests. Based on on-air experience, I believe the results can be used as a rough guide to determine which modes will work when others fail.
There can obviously be several types of ionospheric disturbances along a path so the possibilities are beyond the capabilities of the simulations. In other words, "your mileage may vary". If these tests reveal anything, it's that mode sensitivity alone cannot overcome ionospheric distortion. Signal spread and timing can make a very sensitive mode fail while a less sensitive one keeps printing. There are several examples of this below. It's worth noting that some are more 'distortion sensitive' than others where only a slight bit of frequency spread and path delay will cause decode problems. These are obviously not the best for long-haul contacts where the chances of ionospheric distortion become more likely. Generally speaking, the ionosphere is stable most of the time so the majority of the modes mentioned work just fine most of the time. Thankfully, we have the ability to choose one that works best when the ionosphere throws a curve. Hope the "Guide" is useful. Suggestions / feedback welcome. Tony, K2MO PS: Thought I'd mention MFSK31 for those want a fast mode with a tolerance for adverse conditions. See http://mmhamsoft.amateur-radio.ca/MMvari/ _____________________________________________________ Sensitivity Test - Direct Path (no ionospheric disturbance) Minimum SNR for 100% copy Contestia 500/32............-15db DominoEX-4 ..................-15db THROBX-4......................-15db MFSK16...........................-14db THOR11...........................-14db RTTYM**...........................-13db Contestia 500/16............-13db CW 20 WPM...................-13db*** THOR16...........................-12db Olivia 500/16 ................. -12db MFSK31*........................-12db Olivia 500/8.....................-10db PSK31............................ -10db DominoEX-11...................-8db MT63 1K............................-8db Olivia 500/4...................... -8db PSK63..............................-7db Feld Hell............................-7db RTTY 45............................-5db * MFSK 31.25 baud. MMVARI Software. ** Intermittent decode problem with RTTYM regardless of SNR *** Subjective - speed dictates SNR ______________________________________________ Sensitivity Test - Direct Path -12db SNR (no ionospheric disturbance) Percentage of decode for modes with SNR threshold above -12db Olivia 500/8.... ...................90% Olivia 500/4........................90% DominoEX 11....................90% PSK31................................90% PSK63................................20% Feld Hell............................readable* MT63 1K...........................no copy RTTY 45 baud..................no copy * faint text - readability would depend on QRN _______________________________________________________ Sensitivity Test - Direct Path (no ionospheric disturbance) Percentage of decode for modes with SNR threshold above -15db MFSK16.......................95% Contestia 500/32.........95% Olivia 500/16...............90% Thor11..........................80% RTTYM..........................80% Contestia 500/16.......<50% DominoEX 11bd........<50% Olivia 500/8.............. <50% MFSK31....................<50% PSK31........................<50% Feld Hell......................No Copy MT63...........................No Copy Olivia 500/4................No Copy PSK63........................No Copy RTTY 45......................No Copy THOR16......................No Copy _______________________________________________________________ High-Latitude Moderate Disturbance - 3ms path delay - frequency spread 10Hz - SNR -8db) Contestia 500/16........100% CW 20 WPM...............100% MFSK16......................100% MFSK31**...................100% Olivia 500/16...............100% Olivia 500/8..................100% RTTYM 500/32.............100% Olivia 500/4....................90% Feld Hell..................... ...90%* ThrobX-4........................70% DominoEX 4bd..........No Copy DominoEX 11bd........No Copy PSK31.........................No Copy PSK63.........................No Copy RTTY45........................No Copy THOR-11.....................No Copy THOR-16.....................No Copy MT63............................No Copy *diffuse print - readable ** MFSK 31.25 baud MMVARI Software. _______________________________________________________ High-Latitude Disturbed - 7ms path delay - frequency spread 30Hz - SNR -3db ) Contestia 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% DominoEX-4..............no copy MT631K......................no copy PSK31........................no copy PSK63........................no copy Thor-11.......................no copy ThrobX-4....................no copy Feld Hell.....................readable * * diffuse print - readable ** Intermittent decode problem with RTTYM ________________________________________________________ Mid-Latitude Disturbed - 2ms path delay - frequency spread 1Hz - SNR -8db) Contestia 500/16.......100% MFSK16.....................100% Olivia 500/16..............100% CW 20 WPM................90%* DominoEX 4bd............90% Feld Hell........................90% MFSK31 ....................90% MT63 1K.......................90% Olivia 500/8..................90% Olivia 500/4..................90% RTTYM 500/32.............90% ThrobX-4.......................90% DominoEX 11bd..........80% Thor-11..........................80% Thor-16..........................70% PSK31...........................70% PSK63...........................50% RTTY45.........................20% * Missing Morse elements due to selective fading ______________________________________________________________ Low-Latitude Disturbed - 6ms path delay - frequency spread 10Hz - SNR -8db) Contestia 500/16.....100% MFSK16...................100% MFSK31...................100% Olivia 500/16............100% RTTYM 500/32..........100% CW 20 WPM..............90% Olivia 500/8................90% Olivia 500/4................90% Throbx-4......................70% Feld Hell....................Poor Copy* DominoEX 4bd .......No Copy DominoEX 11bd......No Copy MT63 1k....................No Copy PSK31......................No Copy PSK63......................No Copy RTTY45.....................No Copy Thor-11bd.................No Copy Thor-16bd.................No Copy * Characters diffuse difficult to read. Readability improves with increased SNR
