jj@rabbit.UUCP (07/03/84)
First the nit: Color TV frequency horizontal sweep is at 15.735 kHz. This allows the harmonics of the sweep frequencies to line up so that they miss the color subcarrier and the audio subcarrier both. (Aside: 2 * 15.735 kHz /3 /5 /5 /7 = the vertical sweep rate. Exactly.) As to servicing comments, I've been known to measure the SPL from various switching supplies/etc and send back a report along with some EPA figured. <OUCH!> Stamp out loose flybacks! -- EVEN TEDDY BEARS HAVE SECURITY BLANKETS! "It's beefsteak when I'm hungry, and whiskey when I'm dry, It's a greenback when I'm hard up" (allegra,harpo,ulysses)!rabbit!jj
dmmartindale@watmath.UUCP (Dave Martindale) (07/04/84)
I'd like to pick a nit with jj's nit-picking. The colour subcarrier frequency is C = 3579545 Hz, +-10 Hz - this is picked, as he says, to keep the sound and video from interfering with each other as much as possible. Then, the horizontal frequency H = C*2/455 which is about 15734 Hz. This makes the colour subcarrier an odd multiple of half the line frequency, reducing interference of the colour and luminance information (and giving the best black&white picture). Finally, the vertical frequency is H*2/525 (525 lines, 2:1 interlace) which is about 59.94 Hz. But of course, terminals don't necessarily use exactly the same frequencies that broadcast TV does. As long as they use frequencies in the same ballpark, they can use the same (cheap) TV parts in their monitors. It's possible to build terminals that use ultrasonic horizontal frequencies, but few manufacturers seem to do it.