Hello Tony, Yes it's true that it is a very interesting problem. For this, it exists services which make soundings on the ionosphere and apply complex algorithms to extract the main parameters of the ionospheric transmission. I suppose that it could be done by specific Hams stations in TX and others in RX (the first ones making soundings and the last ones receiving the soundings and transmitting the results), but we will need a study by a specialist, with soundings to produce, algorithms to use and so on...
For instance, what is possible in front of such phenomenas which can't be expected is to increase diversity (frequency and time as in Olivia) or perhaps diversity of antennas (but a bit complicated in HF)... 73 Patrick ----- Original Message ----- From: "Tony" <[EMAIL PROTECTED]> To: <digitalradio@yahoogroups.com> Sent: Thursday, July 17, 2008 10:01 PM Subject: Re: [digitalradio] Re: F6CTE mode sensitivity robustness > Patrick, > > Apologies for the delayed reply. It's interesting that a sound card > program > could distinguish between the types frequency Doppler caused by the > ionosphere, i.e., travelling wave disturbances, multi-path etc. > > I often see the effects of selective fading sweeping across the spectrum > with wide-band modes like MT63 and was wondering if there's anything we > can > tell about the refracting layers, phase and so on using this mode or > something similar? > > Thanks, > > Tony, K2MO > > > > > > ----- Original Message ----- > From: "Patrick Lindecker" <[EMAIL PROTECTED]> > To: <digitalradio@yahoogroups.com> > Sent: Sunday, July 13, 2008 8:36 PM > Subject: Re: [digitalradio] Re: F6CTE mode sensitivity robustness > > > 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! Groups Links > > > > > > > -- > ~~~~~~~~~~~~~~~~~~~~~ > 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! Groups Links > > > > > ------------------------------------ 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! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! 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