RE: Dopler wave o scope use
Fun it was, too.
Looks to me like a 4st doubles the number of octaves shown, likely from the every-second-revolution exhaust note. The display was more cluttered and busy than I'm used to with 4 strokes, but clear lines were there when the frequencies were restricted on the vertical scale.
The model has a 14x8 prop and is said to tack in the 9K range on the ground. No accurate ground tach available, but it's a clue...
We were able to plug the resulting Spectrogram frequencies into the speed calc xls sheet, which gave us something on the order of 98mph and 11,500 RPM. These numbers jive fairly well with either a slippery ship (she is exceeding geometric pitch speed by somewhere near 10%, which we know can and does happen), or the speed could be somewhat inflated by an improperly flown pass.
I dislike automated software, prefer to measure and plug in values myself. That's why I choose spectrogram/spreadsheet over wave-o-scope. Ask software to make a decision for you, and 7 times outta 10, it'll choose what you didn't want....
It was fun dopplerin' that, Spitz.
J