Hi Steve and all, Here's an update on my tests of decoding weak JT65A signals. I used 1000 files generated by SimJT, each containing one JT65A signal at S/N = -24 dB. I am using current code revisions of WSJT-X v1.6.1 (with minor edits noted below) and WSJT v10.0.
For each line in the following table the final number is the number of valid decodes. None of the tests yielded any false decodes. 1. WSJT-X (BM only) 2 2. WSJT (BM only) 5 3. WSJT-X + kvasd 189 4. WSJT-X + kvasd (thresh0=1, ntest>0) 207 5. WSJT-X + sfrsd (Linux) 302 6. WSJT-X + sfrsd (Win32) 309 7. WSJT-X + sfrsd (Linux, thresh0=1) 348 8. WSJT-X + sfrsd (Win32, thresh0=1) 350 9. WSJT + kvasd (Linux) 809 10.WSJT + kvasd (Win32) 809 Test 4 set thresh0=1.0 rather than 1.5 in jt65a.f90. Tests 5 and 6 used Steve's small changes to demod64a.f90 and extract.F90. Tests 7 and 8 used these and also set thresh0=1.0. Tests 9 and 10 used the default WSJT v10.0. I believe the small differences in tests 5-6 and 7-8 are the result of using different random number generators in Linux and Windows. (The resulting random numbers generate the stochastic erasure patterns used in Steve's algorithm.) Unless I've made a mistake somewhere, these results show clearly that for marginal, isolated signals, none of the decoding schemes currently being tested in WSJT-X reach the sensitivity provided by WSJT 10.0. To me the decoding superiority of WSJT is surprisingly large, even though it probably amounts to slightly less than 1 dB. (See, for example, the steep curves for "percent copy vs. S/N" in Figure 4 of http://physics.princeton.edu/pulsar/K1JT/JT65.pdf or Figure 2 of http://physics.princeton.edu/pulsar/K1JT/K1JT_eme2006.pdf .) It seems we would be well advised to look in detail at the (probably rather minor) code-tuning differences in the late stages of processing JT65 signals in WSJT and WSJT-X. An important question will be whether we can simultaneously obtain near-optimum weak-signal sensitivity along with acceptable decoding speed and all-around performance in a band filled with many signals. It should also be instructive to try sfrsd as the final JT65 decoding step in WSJT 10.0. -- Joe, K1JT ------------------------------------------------------------------------------ Monitor Your Dynamic Infrastructure at Any Scale With Datadog! Get real-time metrics from all of your servers, apps and tools in one place. SourceForge users - Click here to start your Free Trial of Datadog now! http://pubads.g.doubleclick.net/gampad/clk?id=241902991&iu=/4140 _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
