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Mike Richter wrote:

> At 10:08 AM 6/19/2005 -0700, John Ross wrote:
>
> >or 2) Very low-level audible RF interference on the recording itself that
> >comes from a local radio station, including the location (e.g., the station
> >ID) and the date -- maybe a newscast that begins, "It's Tuesday, August
> >third 1954, and I'm Announcer's Name with the news for Heaving Springs..."
> >or a unique news story that can pinpoint the date, such as a big fire or an
> >election. Or maybe the recording itself might be an off-the-air tape from
> >the local radio station which the original recordist let run to include the
> >station ID and date before the tape ran out.
>
> If the issue is determining Europe or the U.S., the solution is even
> easier: measure the hum. There's almost always residual hum and 50 Hz (and
> harmonics) can easily be separated from 60.
>
> Mike
> --

Or 25-cycle hum in Toronto in the late 40s to early 50s.....like on the unheard
Art Tatum tapes made here in 1949. (Unheard because people talk all through
them, by the way.)

dl