phil@ux1.cso.uiuc.edu (05/19/89)
> I've heard that you can turn on a Class A device in your home, but if > you interfere with someone's TV or receiver, the FCC can force you to > stop using your device, or modify it to stop interfering. Amateur ham > radio operators run into this often. What hams often run into is the misunderstanding about the difference caused by these two sources of electromagnetic radiation. Computers, which have sharp electrical pulses, radiate energy over a very broad spectrum. They radiate on every TV channel (even the cable channels) and just about every radio frequency. A filter attached to a TV set cannot eliminate the interference without eliminating the undesired signal, which looks just like the TV broadcast. Hams, on the other hand, are restricted to transmitting only within certain frequencies established by FCC rules (list available if you are interested). As long as the ham is using a properly operating transmitter, signals outside of ham bands are significantly reduced. If such signals are outside of the ham bands (even if lower than the levels the FCC requires), it is the ham's responsibility to correct the problem. If, on the other hand, the signals that cause the problem are inside the ham bands, then it is the fault of the receiver or TV set, and the correction has to be done there. Although most hams will volunteer their technical experience to solve such problems, in many cases with today's cheaper and cheaper plastic cased devices, these problems are unsolvable. Hams do often have a different problem. We like to use computers in our ham shack, but even a class B computer will readily wipe out the weak signals hams receive from all over the world, from satellites, and even from the moon. > Does anyone know more about this topic ? Some very competitive brands, > like ALR, are class A, and would make a terrific buy, if only one could > be sure of being able to turn them on at home. There are enough > Class A PCs on the market that it would be helpful to know what can be > done about the Class A bummer. If you live far enough away from other people so that the radiation does not reach them, and can live with the effects on your own TV or other devices, then you don't really need to worry about it. If not.... > One way of turning a Class A into a Class B is to put conductive paint all > over the inside of the box; any experience with this ? It won't give the computer the FCC certification, but it could very well meet the FCC requirement to correct the problem. The certification is only needed to sell the unit to the consumer/home market, not to actually operate it in your home. Even the Class B certification does not make it the problem of the onwer of the TV to correct any problems, although it could suggest the manufacturer get into the act, which is unlikely to be the case for class A since those units are "not intended" for consumer/home use. > ---------------------------------------------------------------------------- > P.S.: if you MUST email a reply, please don't bother including the FCC's > number. I have it, but feel embarassed to ask about fines/jail terms. That of course will depend on intent and other factors. Captain Midnight (infamous HBO pirate) got off with a few $K fine and lost his ham license (every group has some bad apples, hams call them "lids") for a year (and probably no hams will still talk to him). The FCC mostly tries to stomp on people causing intentional and malicious interference, and that goes for companies selling uncertified computer equipment. If you want more information, go to a library with federal documents, get Code of Federal Regulations, Title 47 (book 1) and look up Part 15. --Phil Howard-- (KA9WGN, ham tech class) <phil@ux1.cso.uiuc.edu>