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Originally Posted by blue_lateral
I've wondered about that but never tried it. I have read that most of the interference comes from the color burst, but this method would also remove the chroma information from the video. I think after color was common, they just built b/w sets with no high frequency response in the video amplifier to avoid the chroma interference. On older sets capable of a really sharp b/w picture, the interference would be worse.
wa2ise- How is the overall quality of the video? There is no over-the-air HDTV where I live yet. The quality of over-the-air analog here is pretty bad. I had high hopes that HDTV converters would finally be a high-quality signal source for these older sets. There is another thread going that suggests the quality is terrible. What do you think of yours?
John
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Hi John, the quality of true HD is excellent, but the source at the TV station has to be excellent as well. Sports events like the SuperBowl are usually excellent, but other material recorded at low resolution will never look good. If you can get HDTV over the air reception the quality of the image will be great. But there is the "cliff effect", either you get perfect images or nothing at all. Oh, there is a narrow region between the two, where you'll see the image literally break up and studder, but no ghosts.
Sure you have no HDTV service in your area? Most over the air NTSC stations have HD service that covers substantially the same area. But if your NTSC reception is poor, you might not have HD either. But most HD is transmitted in the UHF band, and a highly directional high gain UHF antenna might bring in the HD, as well as your NTSC UHF stations. If you can get decent NTSC that way, the HD should work.
There's always cable HD and satellite, but those cost subscription fees. Also be aware that digital cable and satellite use different transmission standards than over the air uses. So an "over the air" box won't work on cable or satellite.
As for the use of the "Y" green RCA jack on the HD receiver box, that will work *IF* you setup the HD box to convert all digital reception to "480i". My box provides NTSC (composite and S video) on separate jacks from the VPrPb high def jacks at the same time.
You could convert an old roundie to display HD, but you'd have to modify the horizontal deflection circuits to operate at 32KHz (1080i) or 43Khz (720p). This is not trivial. Especially when you consider the convergence and pincusion circuits (for a color roundie of course). Also the video amps would need more bandwidth. But for a B&W roundie all you really need do is change the timing circuits of the horizontal oscillator. A potential problem is that the B+ boost and the very high voltage may change too much (duty cycles would be different) You'd have a lot of overscan, but that's not serious in that the display area is 4 by 3 instead of 5 by 3. But you'd need extensive TV experience to pull it off successfully. As for a color roundie, this is a case where pulling the chassis (and storing it for later use in a restoration) and installing a VGA monitor's CRT and circuit boards in place of it would make more sense. If it's an older one with real pots for contrast and brightness you could remote those pots where similar ones served the old chassis. You should be able to reuse the old tuner to then feed its IF into the IF of the HD receiver box (which you'd also hide inside the console) so it would still work as normal. A tube audio amp (fed by the same power supply you'd build for the tuner) could be used to keep that "tube" sound the old chassis had. Using the same volume control from the old chassis. So it could be done, might as well use that nice old cabinet that is missing the old CRT or chassis...