[BC] FM Stereo invention

[Andy Green Listservers]

Ah Yes, this discussion is stirring up some old memory cells..

Back in the 70s and early 80's. many stations here in Ireland didn't have
the money to buy stereo generators, let alone an Optimod with one built in,
so we used to build our own - there were two principal designs doing the
rounds, as I recall, one, based on a matrix design by Trevor Brook, of
Surrey Electronics in the UK, (which he published in Wireless World in
1977), and another which was a more rough and ready switching design, a TTL
or CMOS switch driven by a divided down 2.something MHz off-the-shelf
crystal from an electronic parts catalog- the result was  a pilot tone error
of something like 40 HZ. There was no lowpass filtering of the output,
although there was a PI filter of the pilot. 
There was no attempt to correct for pilot phase. Some switching designs did
try to inject a little more L+R into the mix, but most didn't bother- the
extra L-R made the stereo sound 'wider'!



Andy Green
 
Total Broadcast Consultants Ltd.,
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Waterford Business Park,
Cork Road,
Waterford City,
Ireland.
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-----Original Message-----
From: broadcast-bounces at radiolists.net
[mailto:broadcast-bounces at radiolists.net] On Behalf Of WFIFeng at aol.com
Sent: 20 February 2007 04:52
To: broadcast at radiolists.net
Subject: Re: [BC] FM Stereo invention

In a message dated 02/19/2007 9:22:52 PM Eastern Standard Time, 
rorban at earthlink.net writes:

> (4/pi)[(L-R)COS(ws)+L+R]
>  
>  One can now clearly see the matrix representation, with L+R at baseband 
and 
>  L-R as a double sideband suppressed carrier AM signal generated by 
>  multiplying L-R by COS(ws).
>  
>  (The 4/pi is a trivial gain factor).
>  
>  Please note that these equations do not assume a sample-and-hold 
operation. 
>  Such an operation is unnecessary.

All I can say is that I truly thank God for very intelligent folks like 
yourself & Frank Foti, and so many others here, who fully understand this
stuff and 
make it almost look easy. :) Me, I just grasp the *concepts*. I think of
this 
in terms of what I have seen on an oscilloscope & spectrum display. You've 
got the nitty gritty down to a science, literally. That's going well below
the 
"surface", where I'm at! I'm a tinkerer, you're an order of magnitude beyond

that.

Man, I love this... I really do! It leaves me scratching my head in 
amazement! Thank you! :)

Willie...
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