Hello Joe, during the winter 2012-2013 I used JT9-2 with succes on 500 kHz. Running only 4 Watt TX power into a 11m high and 20m long inverted-L antenna (estimated ERP about 30 mW) I managed QSO's up to 2000km. JT9-2 for sure outperformed JT9-1, but maybe not by the full 3dB. 12 minutes for a QSO is very acceptable on 630 meter, using QRSS (very slow CW with 3-10 seconds dotlength) a QSO takes at least half an hour. This february I managed to work N1BUG on 630 meter in JT9-1, that QSO took 95 minutes and was preceded by several nights of failed attempts.
But I do understand your point of view and agree with the fact that time is better spent on improving S/N decoding treshold by implementing new techniques rather than going backward. I am looking forward to this new developments and will be eager to use them on 630 meter. 73, Rik, ON7YD - OR7T ________________________________________ Van: Joe Taylor <[email protected]> Verzonden: donderdag 6 september 2018 16:51 Aan: WSJT software development Onderwerp: Re: [wsjt-devel] JT9-2 mode? Hi Rik, We are well aware that propagation-induced signal distortions at LF and MF are very different (and generally much smaller) than at HF. The extremely narrow bandwidths used by discontinued sub-modes JT9-2, JT9-5, JT9-10, and JT9-30 took advantage of these differences and provided sensitivities not otherwise achievable. However, the data rate of these sub-modes was proportionally smaller, as well. A minimal standard QSO takes 12 minutes in JT2 and 3 hours in JT9-30. As a result none of these submodes ever gained any significant use. We now consider JT9 to be essentially a "legacy mode", and we have no plans to bring back JT9-2, etc. In the meantime we have developed better ways of achieving lower S/N decoding thresholds, with new coding and modulation schemes. At present these ideas and tentative plans are on the "back burner", but we may return to them in due course. Of course, all of our past code can be recovered from the open-source archive. With dedication, someone with enough time and interest could resurrect what's needed to make a working platform for JT9-2, JT9-5, etc. I do not recommend this approach, because better schemes are possible. -- 73, Joe, K1JT On 9/6/2018 2:59 AM, Rik Strobbe wrote: > ​Hello, > > I hope I am at the right place with my question (if not so, please let > me know where I need to be). > > I am using JT9 on the 630 meter band (472-479kHz), it is an excellent > mode to work distant stations. But even with JT9 is is very difficult to > cover distances of over 5000km. > > At these wavelength it is a hard job to get some signal radiated > (antennas are very small compared to then wavelength), so most stations > have an ERP of less than 1W. > > In addition, depending on the countries, there is a ERP limitation > between 1 and 5 W EIRP. So increasing the radiated signal is often not > an option. > > In an early version of WSJT-X several "flavours" of JT9 were available: > JT9-1 (1 min sequence), JT9-2 (2 minutes sequence) and JT9-5 (5 minutes > sequence). > > JT9-2 would give an extra 3dB (more or less), very often the difference > between success and failure on 630m DX. > > I believe JT9-2 and JT9-5 were abandoned because there were issues with > the doppler shift and multi-path propagation on HF, but this is less > critical on lower frequencies and on 630m at least JT9-2 was very useful. > > Question 1: Is the early version of WSJT-X (that supports JT9-2 and > JT9-5) still available somewhere? > > Question 2: Would it be feasible to implement JT9-2 and eventually JT9-5 > in a new version of WSJT-X? This would also take advantage of > the decoding improvements made the last years. > > 73, > > Rik, ON7YD - OR7T ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ wsjt-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wsjt-devel ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ wsjt-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wsjt-devel
