andrew@garfield.UUCP (Andrew Draskoy) (07/27/83)
From: garfield!andrew (Andrew Draskoy) Newsgroups: net.audio Title: video terminals VS cassette tapes Article-I.D.: garfield.447 Posted: Wed Jul 27 01:20:53 1983 Here's a question for all you audiophile hackers: I've been told that most video terminals give off various forms of electro-magnetic radiation. Do I need to fear for my cassettes when I have them near my terminal? Andrew Draskoy {allegra, ihnp4, utcsrgv}!garfield!andrew
brian@sdcsvax.UUCP (Brian Kantor) (08/04/83)
On terminals with steel cabinets, no fear, the cabinet will contain the magnetic fields pretty well. It wouldn't be smart to store your cassettes on top of it, though. On plastic (sigh) VDTs, there are several magnetic fields inside that might get out: the field from the deflection coils that sweeps the electron beam around the screen; the field from the "flyback" transformer that generates the high voltage to light up the screen; and the field from the power transformer. It's in the manufacturer's own best interest to control the escape of these fields from the components that use them, simply for efficiency reasons (wasted energy), but some escapes anyway. These fields do decrease rapidly with distance, but sometimes those coils and transformers are pretty close to the cabinet faces. Most telephones are not very well shielded magnetically either; this is not to suggest that they represent a danger to cassettes, but rather as a means of testing your terminal. Just put your phone on top of your crt, and if you hear buzzing, whistles, high-pitched (~ 15Kc), or hum during a conversation that goes away when you move the phone or turn off the terminal, chances are pretty good that the cassette wouldn't like it either. This is a quick and dirty test, with no guarantees, but since most everyone has the necessary test equipment (until Ma Bell get her rate increases), it might be worth trying. (By the way, the magnetic fields generated by a telephone are extremely weak, which is why they generally are not well shielded - they don't have to be!) -- Brian Kantor, UCSD. {philabs,ucbvax} !sdcsvax!brian sdcsvax!brian@nosc