Hallo Andrew
FYI, I have exactly the same problem as tomh with downloading the calibration file, my serial is D11310006 so it is not starting with a zero…
I manually placed the calibration file from a previous installation in the cal_files directory and Spike seems to like it 😀
Strange thing is that i had the same error a few years back when installing SignalHound v2.18b, after looking in the calibration it seems to be an 404 error page, i remember it was hosted by HostGator!…
Grtzz Mark