Re: Would you accept constrained PSK31 operating procedures?


moshecontra
 

First, PSK31 is NOT a frequency-shift modulation scheme.  It is PHASE shift.  In the simple (and most commonly used) BPSK mode, the phase is simply flipped 180 degrees - the frequency stays exactly the same.  (There is another mode, QPSK which shifts 90 degrees, that has some advantages, but is rarely used AFAIK.)  But in addition to the phase flip, in order to eliminate wideband splatter, the envelope is modulated, so that ahead of the phase flip the amplitude decreases gradually to zero, then the phase flips, then the amplitude increases smoothly to full power again.  If the envelope has the ideal sinusoidal shape, an "idle" PSK31 signal (a string of many zero bits) is therefore mathematically identical to a "two-tone" signal, i.e., two carriers that are about 32 Hz apart, beating with each other.  That's why it sounds like a warble.  The phase flipping is easy to add to a CW transmitter.  The correct amplitude modulation is the harder part.

Second, I am looking for a way to do it all with simpler equipment, not more complicated!  No Arduino for me therefore...  :-)  I can simply use my SSB rig and any old PC, but still would like to be able to do it with a CW transceiver.

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