Okay, this may seem prebasic. I've been playing in PSK31 a bit in the last couple months. It suddenly occurs to me the RST system, originally develped for CW, may not be entirely appropriate for modern computer driven digital modes.
(R) if I'm getting every character = 5, when is he a 4, with 90% copy? 95%?
(S) thats easy, look at the S-meter. But then again, I've had a couple of smashing 100% copy QSOs from guys with S5 signals......given the low power nature of most PSK sigs.
(T) used to be known as "tone", there is no tone with PSK. I could perhaps substitute the term "Tramline"? Does the tramline signal on the waterfall look strong & clean? I have not master the concept of IMD using Digipan.....is there a connection?
Some of this seems very subjective. On the one hand I want to send the guy a nice sig report, on the other hand I question my own "interpretation" of the RST system as applied to PSK.
Has anyone ever thought of another signal report system for PSK or other computer generated digital modes........Any comments? questions? rude noises?

hihi
cheers........David