Hello Tony, >While on this subject Patrick, I wanted to ask if you thought it was possible >to create software that could measure ionospheric disturbances >such as >frequency Doppler / spread? I'm not a specialist, but here is my opinion.
Ionospheric Doppler modulation (which applies badly on PSK transmissions): yes theorically it would be possible to calculate the variation of phase (outside the standard variation of phase of 180 °) per unit of time. However, if you receive a strong PSK transmission and read a bad quality figure for it (in Multipsk, from 0 to 5/5), it is certainly due to the Doppler (however it can be also caused by multipath). As Doppler is random, it can't be taken into account in some equalizer. Spread due to multipath: it is more complicated as you must identify the channel transfer function. However once done, you could take into account the channel function (through an equalizer) and improve the decoding. 73 Patrick ----- Original Message ----- From: Tony To: digitalradio@yahoogroups.com Sent: Sunday, July 13, 2008 10:06 AM Subject: [digitalradio] Re: F6CTE mode sensitivity robustness Patrick, Thanks for the suggestions. I did try manipulating PSK31 to run at roughly half speed. I changed the baud rate to 16.5. The sensitivity increased by 2 to 3db (according to the path simulator). While on this subject Patrick, I wanted to ask if you thought it was possible to create software that could measure ionospheric disturbances such as frequency Doppler / spread? The PSK31 tuning indicator found on most software seems to show this by indicating a rapid shift in frequency. Another kind of "dial" or graphic might be useful or maybe just the data; frequency spread in Hz, Hz/sec etc. A steady signal source like WWV might be useful for this kind of measurement as well. Tony, K2MO ----- Original Message ----- From: "Patrick Lindecker" <[EMAIL PROTECTED]> To: <digitalradio@yahoogroups.com> Sent: Saturday, July 12, 2008 5:39 AM Subject: Re: [digitalradio] Re: KV9U - Mode Sensitivity / Robustness Hello all, Another Patrick here. For an honest comparaison, logically the result might be normalized to a standardized text throughput (based, for example, on BPSK31). For example, the Olivia 32-1000 has a throughput of 24.4 wpm. MFSK16 about the same as PSK31 (a little less than 50). This because, it is mechanical to improve a minimum S/N: if you decrease the speed transmission by 2 you have a gain of 3 dB on the minimum S/N (however in the reality it is only about 3 dB because the new parameters are not at the exactly same quality of "optimality"). Note: a word is a group of 6 characters. In fact, it is not totally honest, because characters can be 6, 7 or 8 bits large and of course the more bits you have and better it is (with 8 bits you can transmitted accented latin characters or non-latin characters, when you can't in 7 bits and in 6 bits you cannot distinguish small or capital letters). Now to normalize it is easy. For example, if the text throughput is half the normalized text throughput, the determined minimum S/N is increased by 3 dB and so on (10* log(ratio)). 73 Patrick (F6CTE) ----- Original Message ----- From: Patrick Novak To: digitalradio@yahoogroups.com Sent: Saturday, July 12, 2008 9:06 AM Subject: Re: [digitalradio] Re: KV9U - Mode Sensitivity / Robustness Yes... that would be the ONLY proper test... the statistics would tell us... cheers P Tony wrote: Patrick, I for one would like to try different modes and compare them under real conditions. There can be too many variables. I agree, I think the simulator can tell a lot about mode performance, but it has it's limitations. It might be a good idea to test modes according to type. Seems fruitless to compare a mode that's known to be extremely sensitive and robust against the "average" chat mode. Good point about switching frequency when testing; need to mind the wide modes in the narrow band segments etc. There was a lot more activity along these lines when sound-card modes were first introduced. Wonder if anyone recalls digital beaconing? Station S59DOR had one on 10 meters that would transmit the different Hellschreiber modes. Macros allowed the software (IZ8BLY's Hellschreiber) to switch modes automatically. Have a screenshot of the beacon if anyone is interested. Glad to see the enthusiasm Patrick! It's the stuff that keeps the hobby alive. Tony, K2MO Kings Park, NY ----- Original Message ----- From: "Patrick Novak" <[EMAIL PROTECTED]> To: <digitalradio@yahoogroups.com>; <[EMAIL PROTECTED]> Sent: Friday, July 11, 2008 11:09 PM Subject: Re: [digitalradio] Re: KV9U - Mode Sensitivity / Robustness Hi Tony and it is good to see your posting to the group. I for one would like to try different modes and compare them under real conditions. There can be too many variables. I understand it is impossible to do it exactly but how about this scenario: We will start a contact and send a short file in one mode, then switch to a different mode (close/same frequency/band) and send the same file again. Try several modes and then compare the number of errors in each mode. If we have a large sample set we will be able to make an educated guess at the mode which performs best. There could be a group or individual who will keep the results table, or each or OF us (experimenters) will keep own statistics. What do you think? What everybody thinks? regards es 73 Patrick VK2PN 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. -- ~~~~~~~~~~~~~~~~~~~~~ Patrick VK2PN QF56pe Sydney Australia ------------------------------------ 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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