RCU Forums - Spectrogram and Doppler speed?

I’m using a program called Spectrogram and a corresponding spreadsheet that I downloaded on my computer several years ago to calculate speed based on Doppler shift. How accurate is this program? Is there a better way to analyze high speed passes and compute speed? I think I’ve read about a German program that’s out there, but is the Spectrogram and spreadsheet method just as good? I have three good passes that yielded good clean graphs on Spectrogram and I got speeds around 140 mph. The air temp was 20 degrees Celsius and I’m using a “Factor” of 10. For my three passes, I got Fcoming and Fgoing readings of 701 and 502; 682 and 486; 670 and 482. My in-flight rpm was around 17K. Could someone double check my numbers? I could upload the .wav files of the passes if necessary. I would appreciate any insight into this. Thanks.