Re: Dead FM Broadcasting Technologies

[Shawn Mamros <mamros@MIT.EDU>]

>I remember that WODS used FMX for a while. I believe I recall hearing 
>that the manufacturer was affiliated with CBS, so many of their stations
>used it. (103.3 may have begun when they were WMRQ).

IIRC, FMX's proponents came from the former CBS Laboratories (the same
folks who brought you the Audimax, Volumax, etc.).  They were a separate
company independent of CBS by the time FMX came about (though I can't
recall what the company's then-current name was), but it certainly
wouldn't be surprising if they knew the CE's of the CBS O&O FMs...

>I never had an FMX decoding receiver, but I recall that on a conventional 
>FM stereo receiver WODS had severe distortion if you were in an area in 
>which there was the slightest amount of multipath signal reflection. Much 
>worse than common multipath distortion. Some people attributed this to the 
>FMX at the time.

The Bose Corporation undertook a study to prove exactly that point.
There was a fair amount of theory behind it, but they also wanted a
real-world demonstration.  Given Dr. Bose's affiliation with MIT,
they approached WMBR about conducting some late-night tests (at a
time when we'd normally be off the air) with FMX, to which we agreed.

I was at the station the night the testing was done.  It wouldn't
have been the most compelling programming for the average listener
- nothing but repeated playing of a segment of Stravinsky's "Firebird
Suite" while the FMX-equipped stereo generator had its FMX mode switched
on and off - but the Bose people got the recordings they wanted to help
prove their point.

Even better was the reaction of the FMX proponents when the Bose study
came out.  Among their claims were that the tests were flawed because
WMBR's signal represented (in their words) a "contaminated Petri dish".
Needless to say, our technical staff was none too pleased with that
remark, but in the end it didn't matter much.  Whether it was the
Bose study or problems with other real-world FMX installations (such
as WODS's), enough doubts were raised about FMX that the system never
gained additional traction, and ultimately faded away.

-Shawn Mamros
E-mail to: mamros@mit.edu