Re: IGS Monitor from Composite Source?

["Alex Freed" <alexf@mirrow.com>]

"Michael J. Mahon" <mjmahon@aol.com> wrote in message 
RoydnZnvkKYZHKDbnZ2dnUVZ_r6vnZ2d@comcast.com">news:RoydnZnvkKYZHKDbnZ2dnUVZ_r6vnZ2d@comcast.com...
> mdj wrote:
>>
>> There are plenty of chips out there that'll decode NTSC into component
>> forms. I doubt you'd need a lot in the way of support circuitry to
>> drive it.
>
> No, it's a mess.  There are filters and delay lines involved, so any
> chip you find will have lots of pins and lots of external components.
> Chroma separation and demodulation is either an analog process or a
> pretty complex DSP process, so there's no free lunch.


Not quite true. PAL decoding requires a delay line, NTCS does not.
Good chroma/luma separation is done by "comb filters" - get one from an old
but good TV set. Or just use simple filters with band limiting.

Decoding NTSC is not rocket science. There are chips with not too many pins
to do it. I can make a circuit out of about 10 discrete transistors and 4 
diodes
to do the job - like in a TV from the 1960s. Less transistors if I can steal 
the
color carrier  reference (3.58 MHz) from the computer.

A much better RGB signal can be obtained in Apple 2 by digital means :)

-Alex.