We’ve usually mentioned that some technological developments appeared like alien know-how for his or her time. Generally we glance again and assume one thing could be straightforward till we notice they didn’t have the instruments we’ve immediately. One of many greatest examples of that is how, within the Nineteen Fifties, engineers created a colour picture that also performs on a black-and-white set, with the colour units additionally in a position to obtain the outdated alerts. [Electromagnetic Videos] tells the story. The video under simulates varied video artifacts, so that you not solely be taught concerning the particulars of NTSC video, but additionally see a number of the mentioned results in actual time.
Making a black-and-white sign was already a giant deal, with the video and sync offered in an analog AM sign with the sound superimposed with FM. Individuals had demonstrated colour earlier, nevertheless it wasn’t sensible for a number of causes. Sending, for instance, separate pink, blue, and inexperienced alerts would require wider channels and extra complicated receivers, and could be incompatible with older units.
The trick, at the very least for the NTSC commonplace, was so as to add a roughly 3.58 MHz sine wave and use its section to establish colour. The amplitude of the sine wave gave the colour’s brightness. The video explains why it’s not precisely 3.58 MHz however 3.579545 MHz. This made it almost invisible on older TVs, and new black-and-white units incorporate a lure to filter that frequency out anyway. So you possibly can establish any colour by offering a section angle and amplitude.
The ultimate a part of the puzzle is to filter the colour sign, which makes it seem fuzzy, whereas retaining the sharp black-and-white picture that your eye processes as a superbly good picture. If you may make the black-and-white sign line up with the colour sign, you get a pleasant picture. In older units, this was carried out with a brief delay line, though newer TVs used comb filters. Some TV techniques, like PAL, relied on longer delays and had correspondingly beefier delay traces.
There are many extra particulars. Watch the video. We love how, again then, engineers anxious about backward compatibility. Like stereo information, for instance. Though NTSC (generally jokingly referred to as “by no means twice the identical colour”) has been lifeless for some time, we nonetheless prefer to look again at it.
