>>>>> On Sat, 17 Apr 2010 10:37:31 -0700, Brian Lloyd <[email protected]> >>>>> said:
> (I forgot to reply to all.) (I removed one level of > characters below) > On Sat, Apr 17, 2010 at 9:49 AM, Brian Lloyd <[email protected]> wrote: [snip] > It is really Really *REALLY* important to understand what is going on with > these protocols in the presence of propagation anomalies in order to be able > to make decisions about which modes work best under what conditions. My own > recent experiments in monitoring and graphing the phase/frequency changes of > the WWV carrier over time (20-30 minute samples typically) have convinced me > that sequential testing of protocols, i.e. transmitting a message and then > immediately transmitting the same message using the other protocol, is not > likely to produce valid results unless repeated numerous times and then the > results averaged with outliers discarded. True, and I seriously doubt that anyone has bothered to do that. > I have been pestering Dave to do a test version of fldigi that would > let me transmit the same data in two modes at the same time in the > same passband so that both experience *exactly* the same propagation > conditions concurrently. This is somewhat more complex than it sounds... what would work right now would be to generate two audio files (with signals at suitable frequencies of course) and mix them using another program. I'm sure sox can do that in one short command line. In fact if fldigi had xmlrpc methods to start/stop audio file generation, it would be easy to write a script to do an audio file for each mode (for a particular input text), and then you could mix them as needed for your tests. I guess I'll need to write those xmlrpc methods first :-) [snip] > Time to take the next step and build on Chen's work by getting real, > controlled data from live propagation. Some comparisons have been posted to the digitalradio yahoo group. There is one by K2MO, and another by WZ7I. URL for the latter: http://mysite.verizon.net/wz7i/digitalmodes.html The tests done by K2MO are in the files area of digitalradio, and he has posted them to the group a few times too. I can't say how scientific those experiments were, but I know that the path simulator used (pathsim) is GPL'ed so at least that aspect of the tests can be verified by anyone so inclined. ES1HJ also has published some test results but I don't recall if they were on-air or simulation tests. -- 73, Stelios, M0GLD. _______________________________________________ fldigi-alpha mailing list [email protected] https://lists.berlios.de/mailman/listinfo/fldigi-alpha
