[BC] FM Stereo invention

[Mark Humphrey]

On 2/19/07, Bob Tarsio <Bob at broadcast-devices.com> wrote:
>
> Some more FM stereo trivia! It's interesting to note the other contributors
> to the FM stereo effort. Philco, EMI, and Crosby Laboratories also submitted
> systems. There were I believe seven systems proposed in all. Crosby offered
> FM/FM, One proponent offered an SSB sub carrier method, and there was
> another that proposed an AM sub carrier. What a different world this would
> have been if some of these other methods had been chosen.

I researched some of the FM stereo patents a couple of years ago, it's
interesting to see how each inventor approached the problem.  You can
easily view these as PDFs by entering the patent number at:

http://www.pat2pdf.org/

3,257,511 is Dr. Adler's patent for the TDM scheme.  In Fig. 3a, he
illustrated a "rotary switch", turned by a "high speed drive", to
simplify the description of his approach.

3,122,610 is the GE patent filed by Tony Csicsatka, who fled in 1956
from Budapest, Hungary to the US without a job.  A GE recruiter
learned of his talents at a "job fair", he was hired and assigned to
lead their FM stereo project, and the rest is history.

2,851,532 is the FM/FM proposal filed way back in 1953 by Murray
Crosby, and includes an audio matrix circuit.

3,117,186 is the proposal filed by Dick Burden and William Halstead.

Incidentally, both Crosby and Halstead were engineering consultants to
the Rural Radio Network, the early FM network described in this
article I recently contributed to Wikipedia:
http://en.wikipedia.org/wiki/Rural_Radio_Network

3,067,292 is Jerry Minter's FM stereo patent.

An interesting FM stereo receiver patent was awarded to Adrian
DeVries, who worked with Dr. Adler at Zenith.  This includes a 6AR8
beam deflection tube to decode the L-R subcarrier in a synchronous
detector, a technique that's kind of complementary to a TDM stereo
generator.  The circuit description is much easier to follow if you
print the schematic first and follow along; see Figs 2 and 4 in Patent
no. 3,133,993

Mark