If we can stick a phone cable into a modem and digitize a voice, why not stick an antenna into some kind of peripheral and digitize (to a file) a radio signal? Has anyone heard of any such gadget? Now that CPU's can do several hundred megahertz, it may be feasible to catch AM radio of about 0.5 to 1 megahertz, or maybe ham radio.
Those devices already exist, in the form of AM/FM radio tuner PCI cards. They sell for about 20$, but nowadays it's hard to find one without TV-capture abilities, which adds a lot to the price. I don't know much about how to control these cards at a low level, but I suspect the radio program (software on the CD-ROM) uses DeviceIoCtl calls. By disassembling the app you might be able to figure it out. One other advantage: if you have a fast computer and buy one of the TV cards, you can download an app that decodes most scrambled TV-channels for you. (Wonder if it's legal tho? :D)
Larry, try google "packet radio" you'll get alot of info on this.. ham radio guys use this thing to send data from a computer to another in small packets. "the modem is replaced by a terminal node controller (TNC) and the telephone is replaced by an amateur radio transceiver. packet radio takes any data stream sent from a computer and sends that via radio to another amateur radio station similarly equipped." they can exchange files and have they're own bbs ensein This message was edited by ensein, on 5/16/2001 4:42:50 PM
you might also be interested in the "ALOHA" radio network (sp?) that was one of the early influences (50s or 60s?) on networking protocols. errr, if you're into the history of technology ;) i believe it's where they worked out the csma/cd stuff
Interesting. It might not be long before crackers get into downloading garage-door openers, car remote-starters, cell phones, ...:(
sorry to say that people have been stealing those codes for a while. :( which is why some of the new devices use a rotating key system where the sender & receiver change what will be sent thru the air each time via a predetermined algorithm. known (in theory) only to the sending & receiving devices. but now we've plumbed the depth of my ignorance... i know almost nothing about the particulars of the rotating key systems used.
Remote garage door openers are so insecure that some theives would simply get any opener, drive around a nice neighborhood and try it on every house they passed. When a door finally opened (which usually didn't take long), they had their access. You probably already have all the hardware you need to digitize most common AM and FM signals: plug the LINE OUT of your receiver into the LINE IN of your sound card. Bingo! Done. There are lots of interesting signals in the ether you may not know about. Systems like "SCA" (Sub Carrier Audio) have been around since the 50's, they tag on a special mono signal to a FM signal. A special receiver is needed to get them, and as these signals are similar to cabel in you need to pay for them, the receivers are not common. This is usually how "muzak" is broadcast to elevators. "Silent Radio" is another digital system. I beleive it also uses SCA, but transmits a digital signal. These are used in those LED alphanumeric displays to provide content. Here in New York, the state Dept of Motor Vehicals uses it to give people something to read while waiting.