The receiver is now hooked up to a short-wave antenna (G5RV-jr). Presently receiving the 30m QRSS/QSPR band. WSPR decodes with no drift on most stations. I therefore believe that the drift problem is purely cosmetic, maybe it has something to do with warming up, I would not be surprised. No jumps occured up to present.
During my test, for a short periode, the MEPT of I0/N2CQR was visible.
WSPR decodes look like this:
2114 -23 1.4 10.140241 0 F6BIA JN18 33
2116 -13 -0.4 10.140189 0 DH8SA JO53 37
2118 -26 0.8 10.140207 0 PY2GN GG56 37
2120 -15 0.6 10.140106 0 DL0TFK JN48 30
2120 -14 1.2 10.140198 0 DH5RAE JN68 37
2122 -1 2.7 10.140226 1 DL2ZQ JO42 37
Not too bad for a €299.- receiver.
Conclusions would be the following:
I now really like the HF-3W. 1kHz steps are not ideal for ham-radio. The clarifier helps, but is hard to adjust. Using a reference broadcast-station, the carrier can be set to create a 1.3kHz beat tone, that's the offset required for WSPR operations.
The receiver primarily is targeted to yachtsmen. In naval frequency lists, the center frequency between mark and space is listed. The receiver is actually built to help sailors to easily find RTTY stations transmitting weather reports and thus, the frequency display in SSB is off by about 2kHz. Meaning, that the dial for WSPR needs to be set to 14.141MHz with some odd clarifier setting.