Thanks Joe I agree that you have probably pushed JT65 to its limit well below general use for 10 GHz EME and that either an improved JT4 or other options you mention below are the way to invest your effort.
The automatic spreading optimisation feature of the WSJT-X version of JT65c should be useful for terrestrial on 10 GHz. It should work well with tropo-scatter that typically has spreading in the 5-20 Hz range and also automatically optimise for ducting which gets down to below 1 Hz spreading. Just prior to the on-set of ducting we sometimes see a tropo-scatter extension so JT65c on WSJT-X should cope well with all these situations and be the mode I would recommend for 10 GHz terrestrial based on ducting or tropo-scatter or combinations of both. Another useful advantage of JT65c for terrestrial operation is that it has a wider DT tolerance where JT4 has a hard limit of -0.7 seconds. Rex -----Original Message----- From: Joe Taylor [mailto:[email protected]] Sent: Friday, 1 April 2016 12:33 AM To: WSJT software development Subject: Re: [wsjt-devel] WSJT-X v1.7 r6559 Hi Rex, VK7MO wrote: > I note that your conclusion that JT65c is no better than JT4 with > spreading greater than 10 to 20 Hz is based on non-DS decoding. Based > on my tests with r6536 I am inclined to agree that your conclusion > also applies to DS decoding although I would like to do more testing > when a build of r6559 is available. Good! -- additional tests are certainly desirable. > This conclusion does, however, seem to be contrary to the Text books > that the use of higher Mary FSK should improve performance. No question: 64-ary FSK is a more efficient modulation than 2-ary or 4-ary FSK. But it requires much more bandwidth. A JT65 submode with information tone spacing comparable to JT4F would be something like "JT65H", and would need ~20 kHz of bandwidth. > ... At present > averaging is rarely useful on JT4f DS on WSJT-X as the limit is > gaining sync > - thus any improvement in gaining sync should be of significant > benefit to JT4f averaging. > > So in summary I think the next move should be to do some wider tests > to compare the sync performance of JT4f on WSJT10 and WSJT-X to see if > there are options to optimise this mode before you spend time on JT65d. Agreed. I have not put recent effort into optimizing the JT4 decoder, and you have already identified a weak spot to be worked on. Also keep in mind: As I argued many months ago, the best mode for microwave EME may turn out to be a wide-spaced JT9 mode, say JT9G (111 Hz tone spacing, 1 kHz total bandwidth) or JT9H (222 Hz, 2 kHz). These submodes are already partially implemented in WSJT-X. Maybe it's time to complete that effort. Also, Steve and I have been investigating ways to use one of the latest hot things in communication theory -- Low Density Parity Check (LDPC) codes -- for possible application in WSJT-X. So far we have been thinking about a fast mode for meteor scatter, where we need a high rate code, high symbol rate, and bandwidth-efficient modulation. But we could also think about a code that would work well for EME. -- Joe, K1JT ---------------------------------------------------------------------------- -- Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 _______________________________________________ wsjt-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wsjt-devel ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 _______________________________________________ wsjt-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wsjt-devel
