I’m displaying a certain ignorance of technology, that my old age has deemed not worth keeping up with, but I understand that all wireless and remote devices work on the basic principle of sent and received radio frequencies. How easily could these be jammed over several square miles, with a $20 transmitter of a couple of watts broadcasting static on a narrow band of RF at a frequency that would disrupt all the wireless mice or TV remotes or wi-fi cash registers or household electrical meters or self-parking cars?
Remotes for TVs and other electronic consumer goods use infrared. Not really jammable, except within line of sight. For example, direct sunlight on the TV’s remote sensor can make it hard for it to pick up the signal.
I’m not sure what frequency car keyfobs use, but it is RF and not infrared.
Wifi routers and cordless phones use 2.4 GHz and some other bands up to around 6 GHz. These could be jammed. You’d only be able to jam a few at a time, since your jammer would only cover a few channels at a time. Be careful that you don’t hurt yourself, that’s the same band that your microwave oven uses to heat things.
If you did it intermittently and disguised your antenna, you could probably get away with it, since it’s unlikely anyone would realize someone was intentionally causing interference. That band already has a lot of inadvertent interference, due to the many uses. But it would not take the FCC long to triangulate your position once they started looking for your jammer. And you’d get a large fine and probably jail time in a federal prison. They wouldn’t have to catch you actively transmitting–there’s really no non-criminal reason for having a noise generator at those frequencies hooked up to antenna.
Pretty easy to jam, especially FCC open (as opposed to licensed) frequencies. I’ve seen jammers that are about the size and shape as a pack of cigarettes (in fact, they were disguised as a pack of cigarettes in one case). You’d have a pretty limited jamming range though, so your ability to do ‘RF terrorism’ would be pretty small scale and would basically only work on smaller, more isolated WiFi systems.
A modern campus based WiFi mesh system is pretty frequency agile, so you’d need to block out both 2.4 GhZ and 5.0 Ghz and all the channels associated with it to do anything substantial.
I think real ‘RF terrorism’ would be something a bit more involved…something like an EMP. THAT would be nasty, with wide ranging implications and impact. Hopefully no one will be able to pull something like that off (and the sun won’t do it for them) any time soon.
It’s fairly easy to create a jammer for something like wifi and and other things that work on the 2.4 GHz band. The problem is that the inverse square law gets you pretty quickly. The radio power you generate drops off as the square of the distance. So if you build your jammer to be capable of interfering with a signal from 100 feet away, at 1000 feet (10 times the distance) you only have 1/100th the power level. So you need something with 100 times more transmitting power. At 10,000 feet, your power is 1/10,000th what it was at 100 feet. A tiny little transmitter built out of $20 worth of parts ain’t gonna cut it.
Electrical meters only use wifi to transmit data used for billing. If they can’t communicate they still store the data so it’s not like your jammer would accomplish much there. And again you could only interfere with a couple of them at a time unless you really transmit a huge amount of RF power.
As was already mentioned, TVs use infrared and wouldn’t be jammed by an RF transmitter.
I believe most key fobs these days work at frequencies somewhere around 300 to 400 MHz (0.3 to 0.4 GHz), a bit outside of a “narrow band” that would interfere with things like wifi.
Are cash registers wireless these days? I was under the impression that most of those still had wired connections.
The inverse square law gets you with EMP weapons as well. Unless you use something like a nuke, it’s very difficult to make an EMP weapon that has any kind of decent range.
EMP weapons have been promised as the next big thing since WWII, when they were going to stall enemy plane engines and make their planes just drop out of the sky. While they did exactly that under controlled laboratory type conditions, they weren’t so effective in the real world, and for the most part they still aren’t today.
Any good, layperson-level citations for that? I had always (well, for the last 30 years or so. . .) thought that EMPs were a huge danger in warfare. I’d like to read more.
There are amusing anecdotes about what happened when WLW-AM in Cincinnatti broadcast at 500,000 watts, but even that didn’t knock out anything.