Xref: utzoo sci.electronics:5648 rec.video:5927
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pasteur!ucbvax!tut.cis.ohio-state.edu!osu-cis!att!cbnewsc!cptvideo
From: cptvideo@cbnewsc.ATT.COM (david.vlack)
Newsgroups: sci.electronics,rec.video
Subject: Re: MTS Stereo TV Decoder query
Message-ID: <310@cbnewsc.ATT.COM>
Date: 23 Mar 89 16:12:03 GMT
References: <2943@rtmvax.UUCP> <329@carroll1.UUCP> <464@trwind.UUCP>
Reply-To: cptvideo@cbnewsc.ATT.COM (david.vlack)
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 20

I built the RE stereo decoder and found that it indeed can work well,
but NOT AS PUBLISHED. Some minor matrixing errors are easily corrected
in the circuit, but the biggest flaw is the lack of high frequency
expansion circuitry. The article points out the omission and states
that the missing circuitry will not have a serious effect on the
performance. In fact, the lack of dynamic HF expansion completely
destroys the stereo image.
  I made a considerable modification to the circuit to use the
unused half of the NE570 compander chip to provide for the missing
expansion function. That plus numerous changes to time constants
in both the signal and control paths yielded a reasonably good
performing MTS decoder. By using quad op-amp chips the whole thing
can be built on a board area of 1.5 x 2.5 inches and can be tucked
away in an unused space in a VCR. I did that and now enjoy stereo
recording of TV programs on my non MTS equipped HIFI VCR. The NE570
can not exactly duplicate the function of a DBX chip, but it is
suprising how close it can come. I have the modified schematic but
posting it is well beyond the capacity of the ASCII character set.

Regards: Dave Vlack   ...att!iexist!cptvideo