rjung@castor.usc.edu (Robert Jung) (04/06/88)
In article <8803290303.AA02847@mitre-bedford.ARPA> jhs@MITRE-BEDFORD.ARPA writes: > [Lots of stuff about VT-100 emulators deleted] > >With either of these programs, you should use a monochrome monitor if at all >possible, because 80-column emulation on an 8-bit Atari pushes the graphics >resolution to the limit. Next best would be a composite monitor that has a >separate chroma input, or an RGB monitor with an external NTSC decoder >(or just drive the Green input with the Atari luminance signal). Please forgive me if this question sounds stupid or ridiculous (I don't know *anything* about hardware), but do you know where I can buy a commercial NTSC decoder for my 8-bit Atari? If nothing else, how about detailed instructions for making one? Any information will be appreciated, --R.J. B-) ______________________________________________________________________________ Bitnet: rjung@castor.usc.edu "Who needs an Amiga?" = == = = == = Power WithOUT the Price = == = ===== == ===== Just because it's 8-bits doesn't make it obsolete. ==== == ====
jhs@MITRE-BEDFORD.ARPA (04/15/88)
Robert Jung writes: > Please forgive me if this question sounds stupid or ridiculous (I don't > know *anything* about hardware), but do you know where I can buy a > commercial NTSC decoder for my 8-bit Atari? > > If nothing else, how about detailed instructions for making one? I don't know of any commercial boxes, though I would think there would be some market for such a device. However, a cousin of mine who is a video circuit design expert was helping a friend of his design such a box. My cousin decided that, while there are several commercial ICs that are used as NTSC decoders inside TV sets, they all seem to come out with a funny color balance when used on high-quality RGB monitors. He says TV picture tubes are designed to take something very similar to, but not identical with, true RGB inputs. There is some "matrixing" going on, i.e. the signals required at the grid pins of the TV CRT are some funny linear combination of the true RGB signals, and that is what the IC's all produce. If you build an NTSC decoder using the standard ICs, therefore, you get slightly fishy colors. He concluded that the best thing to do was just whip up the decoder "from scratch", meaning using three balanced modulator ICs and his own carrier recovery circuit with PLL etc. I don't know if he ever finished the design, or coached the friend to the point of helping him finish it, but I'll try to find out and report back. If possible, I will try to get him to provide a schematic. My cousin did comment that he had seen enough of an indication of the achievable resolution from the friend's early experiments (with fishy colors) to assure me that if I ever built such a circuit, I would "never want to go back to a composite monitor" on my Atari! Apparently, the resolution is pretty incredible. For a quick fix, though, you might go buy a Commodore monitor and run it with separate chroma input. -John Sangster / jhs@mitre-bedford.arpa