Re: OPT equalising circuit

In article <0BATj.7774$ko5.7767@[EMAIL PROTECTED]
>,
 "Alex" <apogosso@[EMAIL PROTECTED]
> wrote:

> On the stereo-decoder note, what is the phasing of 19KHz pilot with
respect
> to the 38KHz (suppressed) carrier: do the zero-crossings coinside (every
> second one) or peaks coinside (every secon ones)?
> 
> I would guess, the peaks. That way it would have been easier to derive
38KHz
> simply by a class C frequency multiplier.

Your guess is incorrect, the 19 kHz pilot tone and the regenerated 38 
kHz carrier must be phased so that the zero-crossings coincide, that is 
the way the original system specification was written.  If the decoder 
is adjusted so that the peaks coincide it will be impossible to achieve 
any stereo separation at all.  If the phasing is such that the 
zero-crossings do not coincide, but are close, it is possible to achieve 
full separation by adjustment of the matrix separation control, but the 
signal to noise ratio will be degraded.


Regards,

John Byrns

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