The wspr_spread work is excellent.
Doppler Spread
It helped us debug why our TCXO-powered-WSPR beacon was pretty decent on 4m band but flaky on 2m.
Doppler spread value on 70 MHz:
... 70.0924994 VU3CER MK68 23 0 0.29 1 1 0 1 44 1 810 0.517
Now see the problem on 144 MHz:
... 144.4905417 VU3CER MK68 23 -3 0.12 1 1 0 1 39 1 810 0.865
This is quite spread out, but we are operating on 2m, so this is probably expected for a 25 MHz TCXO-based system.
Comparison
A better WSPR generator would produce something like this (dissecting_wsprd sample):
We will get there at a low cost eventually ;)
Update: Based on W3HH on QRZ, this sample recording appears to be from the 30m or 10m band. This explains the "low/tight doppler spread" value for W3HH.