On Thu, 20 Nov 2008 18:16:17 GMT, (Don Pearce)
wrote:

On Thu, 20 Nov 2008 18:03:22 +0000, Goofball_star_dot_etal
wrote:

On Thu, 20 Nov 2008 17:36:49 GMT, (Don Pearce) wrote:



What is that a plot of, and what is the software?


Frequency (r) v rotation of platter (theta) for about ten seconds of
your file, with the start cut off.

Just something I knocked up a few years ago in Labview. 'Software FM
radio'?

OK, I get what you've done. Can you tell me about the number of points
in the sliding sample, windowing etc? I'm thinking those fine wiggles
are probably artefacts of the maths.

d

I don't have it running on this computer at the moment but from
memory.. after demodulation it was filtered with a 60 Hz low pass
filter. I think 1000 points was selected but there is decimation
involved somewhere and I can also choose the window function. It was
a long time ago when I knew how it worked. but it was very well
behaved. I think the fine ripple is real between 40-50 Hz. The biggest
peak was about three times the platter rotational frequency.

Some of the old files I did can still be found at:
http://www.wareing77.plus.com/turntable-web.htm