I'm interested in experimenting with how to non intrusively sniff signals on a wire. Examples are phone lines, VGA video, NTSC video, RS232, etc. One of the first I'd like to try is NTSC video on a standard RG-59 coax. Is there enough radiation from these to detect anything useful if you can get in close ? Or does the coaxial cable effect attenuate it so much that its not feasible ?
Assuming there is enough radiated signal from it to detect something, what is a good technique for doing it ? Use a loop of wire near the cable to detect the field and amplify it ? Wrap wire around the coax ?
I know the questions sound ominous but its really for a good purpose. I'm hoping to apply for a surveillance or electronics related job in a law enforcement field. Right now I've a few semesters of electronics classes behind me and I'm trying to learn some practical things.