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From: agc@briar.philips.com (Aldo G. Cugnini)
Newsgroups: sci.electronics,rec.audio
Subject: Re: Defeating MPX
Keywords: MPX filter tape deck
Message-ID: <1991Jun13.125800.29528@philabs.philips.com>
Date: 13 Jun 91 12:58:00 GMT
References: <1991Jun10.173608.6540@rice.edu> <1991Jun10.175751.6926@rice.edu> <1991Jun12.191926.24744@ee.rochester.edu>
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Reply-To: agc@briar.philips.com (Aldo G. Cugnini)
Organization: Philips Laboratories
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In article <1991Jun12.191926.24744@ee.rochester.edu>,
strong@ee.rochester.edu (John Strong) writes:
|> The multiplex
|> filter is supposed to attenuate noise from FM signals that are
|> being decoded (for stereo separation).

Not quite.  The filter is usually intened to remove the (residual)
19kHz pilot tone from the audio output.  If this signal is strong enough,
it will cause the Dolby encoder to malfunction.

The filter is usually a 19kHz notch filter, but in a cheap receiver could
be just a lowpass filter.


agc