Using a RTL2832U USB dongle, I set up GNU Radio to produce a constellation plot of APRS traffic on 144.8 MHz. The result is what I expected:
So far, so good. Why not try the same thing using the wx GUI instead of the Qt version I had used ? Here are the results... The constellation plot does not look the same at all and it is nothing like the clean QAM constellation I had expected and obtained using the Qt GUI:
Can anyone explain why the wx GUI's constellation plot does not behave as I expect ? Is it simply a case of different default settings and naive user expectations ?