[rec.video] MTS Stereo TV Decoder query

mazda@killer.Dallas.TX.US (John Wilson) (03/16/89)

	I'm searching for information on MTS stereo decoders to add
to my VCR/TV system. I have a Canon HF-600 Stereo VHS VCR that is capable
of recording dual channel audio. This unit has a MPX OUT plug that was
to be connected to a MS-10 Stereo Decoder option that is no longer in
production. 
	Are any such (any brand) MTS Decoders still in production?
	Is the MPX OUT signal a composite FM signal of both audio
channels? The manual simply says this connection is for the MS-10
option but doesn't explain what the actual out-signal is. If this is
a composite stereo (multiplexed) signal, what's the possibility of
my building a decoder using the ECG1655 TV STEREO DECODER Integrated
circuit or equivalent?
	Any information on converting a TV system to Stereo would
be appreciated.

Thanx in advance,
-- 
-------------------------------------------------------------------------------
Moral principles can never be compromised;   |  J.P.Wilson - ...!killer!mazda  
they can only be abandoned.     J.G.H.       |              mazda@killer.UUCP
-------------------------------------------------------------------------------

mazda@rtmvax.UUCP (John Wilson) (03/17/89)

	I'm searching for information on MTS stereo decoders to add
to my VCR/TV system. I have a Canon HF-600 Stereo VHS VCR that is capable
of recording dual channel audio. This unit has a MPX OUT plug that was
to be connected to a MS-10 Stereo Decoder option that is no longer in
production. 
	Are any such (any brand) MTS Decoders still in production?
	Is the MPX OUT signal a composite FM signal of both audio
channels? The manual simply says this connection is for the MS-10
option but doesn't explain what the actual out-signal is. If this is
a composite stereo (multiplexed) signal, what's the possibility of
my building a decoder using the ECG1655 TV STEREO DECODER Integrated
circuit or equivalent?
	Any information on converting a TV system to Stereo would
be appreciated.

Thanx in advance,
-- 
--------------------------------------------------------------------------------
...the greatest sensation of existence, |   J.P.Wilson - ...!rtmvax!mazda     
   not to trust, but to know.    a.r.   |                   mazda@rtmvax.UUCP
--------------------------------------------------------------------------------

tkopp@carroll1.UUCP (Tom Kopp) (03/20/89)

In article <2943@rtmvax.UUCP> mazda@rtmvax.UUCP (John Wilson) writes:
>
>	Are any such (any brand) MTS Decoders still in production?
>	Is the MPX OUT signal a composite FM signal of both audio
>my building a decoder using the ECG1655 TV STEREO DECODER Integrated
>circuit or equivalent?


Well, having been working on just such a project, I can pass the info on to you.

The proper chip to use is the LM1884 (I believe, but I cannot seem to find my
documentation).  The box I've got is in Radio Electronics c. 2/87 I believe.
Might have been 2/88, but...  It was a 2 part article, so Feb and March at
any rate.  There are plans for building an MTS decoder in various methods,
including straight MPX output, modifications to a non-stereo VCR as well as
building a 'probe' (antenna tuned to 4.5 and attached to TV) which will
pass the appropriate information to the decoder box which has a left and
right line level output on it, as well as a headphone jack.  You will probably
want to do some tweaking w/ the box once you get it built, as when you actually
order some of the parts from a person here in Milwaukee, you get what amounts
to an 'upgrade' kit.  The original (article) used an FM stereo decoder...
the LM1884 is a fairly new (less than a year?) chip specifically designed, like
the 1655, for TV stereo.  Good luck!


-- 
"Patience is a virtue, and I'm virtually bankrupt!" - Me
tkopp@carroll1.UUCP or uunet!marque!carroll1!tkopp
Thomas J. Kopp @ Carroll College 3B2 - Waukesha, WI

johng@trwind.UUCP (John Greene) (03/23/89)

In article <329@carroll1.UUCP> tkopp@carroll1.UUCP (Tom Kopp) writes:
>In article <2943@rtmvax.UUCP> mazda@rtmvax.UUCP (John Wilson) writes:
>>
>>	Are any such (any brand) MTS Decoders still in production?
>>	Is the MPX OUT signal a composite FM signal of both audio
>>my building a decoder using the ECG1655 TV STEREO DECODER Integrated
>>circuit or equivalent?
>
>
>to an 'upgrade' kit.  The original (article) used an FM stereo decoder...
>the LM1884 is a fairly new (less than a year?) chip specifically designed, like
>the 1655, for TV stereo.  Good luck!
>
>
Actually the part is not all *that* new as I have a 1984 data book that has that
chip in it.  I would not hold all that much confidence in the article printed in
Radio Electronics.  I was so disappointed in the errors and mistakes in their
designs that I won't even look at the magazine anymore.   
-- 
John E. Greene    "People are just like frankfurters....You have to decide
                   if you're going to be a hot dog or just another wiener" DLR
TRW Information Networks Division 23800 Hawthorne Blvd, Torrance CA 90505
ARPA: johng@trwind.ind.TRW.COM  USENET: ..trwrb!trwind!johng

cptvideo@cbnewsc.ATT.COM (david.vlack) (03/24/89)

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