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PSK31 [Was: Mode A vs. Mode J-FM]



A relatively new mode that was the province of a few diehard DSP
experimenters, mostly in Europe, has just "gone public."  It's called
PSK31.  Peter, G3PLX (aka the developer of AMTOR), has written free
software implementing PSK31 on any reasonably fast computer running Windows
and a standard sound card.  

I know that some other folks--including at least one Amsat-BB
participant--have been experimenting with a similar "BPSK" scheme in North
America.  I have no knowledge of the relative merits of each.  But I
suspect that PSK31's availability on a hardware platform that most of us
already have will count for a lot.

I've played with PSK31 on 20m and 40m this weekend. You can get perfect
copy on signals that would be very difficult on CW, and reasonable copy on
signals you can barely hear.  People say this about each digital mode that
comes out, but this one really digs into the mud on HF like nothing I've
ever seen.  It truly can get through when CW would not.

Could PSK31, or something like it, be an answer for satellite users who
need a robust weak-signal mode that could be used instead of CW?  The
problem is PSK31's required frequency stability, which must be within a
couple of Hz.  That is at odds with doppler shift issues on satellites.
But if some sort of standard rig control were adopted that allowed everyone
to stay constant-frequency at the satellite, with adaptive DSP decoding to
take care of the "fudge factor," such a mode could work on satellites.  The
software already has a bit of the latter in an "AFC" that tracks a slowly
drifting signal.

Much of the cutting-edge techies in our satellite community have been
interested in wideband techniques. And these slow PSK modes have been
worked out for HF conditions, which are different from VHF and up.  But I
suspect you could fit a lot of these narrow (31 Hz) PSK31 signals in an
analog transponder passband :-)  Just a thought.

For those interested, you can find the PSK31 software at:

	http://aintel.bi.ehu.es/psk31.html			(home page)
	ftp://det.bi.ehu.es/pub/ham/psk31/p31sb103.zip  (direct ftp)

73 from KD7MW!
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