eichin@athena.mit.edu (Mark W. Eichin) (11/29/87)
The subcarrier systems (under the tradename StoreCast) are a 38KHz subcarrier off of an FM broadcast station (19KHz is for the L-R signal.) Thus, anything that can interfere with normal FM transmission should do the job here; note that it would be equally illegal.[1] A StoreCast receiver can be built with only slight modifications to any `well-built' FM stereo unit, I even purchased a kit somewhere that had an extra amplifier stage that you could tap into your FM unit to receive such broadcasts, with the reminder that you cannot use the gadget in a commercial manner. If you were to build such a jammer, wouldn't you need so much power that it would freak the electronic cash registers, if you got too close? FCC Class A & B regard emissions, not absorption; the last REALLY shielded machine I saw was the IBM 9000[2] `lab workstation' which was this 68K based un!x box that could be safely run next to an induction furnace... Actually, TEMPEST requirements deal with that, I suspect, if you can find someone to tell you :-) Mark Eichin <eichin@athena.mit.edu> [1] Speculation: a walkman(tm) jammer that simply induced a signal in the headphones directly would probably not be illegal, because of the (presumeably) low power needed? You can generate alot of EMF in a 5 foot antenna wire... [2] I saw this 4-5 years ago at an IBM demo in CT somewhere, in a division that may not exist anymore; I may have the number wrong. Reply by mail if you want more specifics on what I think I saw. Disclaimer: I think these are my opinions, but don't quote me on it ;-)
ron@topaz.rutgers.edu.UUCP (11/29/87)
It's still illegal. Malicious interference is one of the big no-no's despite how compliant your transmitter is with FCC Regulations. -Ron