Building a radio transmitter to interfere with a station

[Akihiro]

Rather curious to know whether anyone here tried to build a radio wave transmitter and intercept a radio station by sending radio waves of similar frequency to that of the radio station. I imagine that would be quite a fun thing to do.

 

[HallsofIvy]

Jamming it? Sure that's been done.

However, radio waves are not a pure sine wave: AM modulates the amplitude so to get cancellation you would have to send exactly the same signal- in other words, you would have to be sending exactly what the radio station was. Of course, even then you would get complete cancellation only at the midpoint between the two transmitters.

FM, frequency modulation, basically requires the same thing.

 

[imabug]

Probably not something I would advise anybody trying just for kicks and giggles

For one, most countries probably make this kind of signal hijacking illegal, and you'd likely get into a lot of trouble for doing it. At the very least, it will cost you a bundle in fines.

Commercial radio stations broadcast using transmitters typically in the hundreds of kW range. Unless you're at the periphery of a radio station's range or your listeners are really really close, your radio signal is just going to be noise superimposed on the radio station's signal.

I can't imagine that it's going to be easy to buy sufficiently powerful transmitters to hijack any radio station's signal. It's certainly not something your corner electronics store is probably going to stock. And the companies that do sell the more powerful transmitters probably want some kind of proof that you have a license to broadcast a signal.

 

[Akihiro]

Probably not something I would advice anybody trying just for kicks and giggles

For one, most countries probably make this kind of signal hijacking illegal, and you'd likely get into a lot of trouble for doing it. At the very least, it will cost you a bundle in fines.

Commercial radio stations broadcast using transmitters typically in the hundreds of kW range. Unless you're at the periphery of a radio station's range or your listeners are really really close, your radio signal is just going to be noise superimposed on the radio station's signal.

I can't imagine that it's going to be easy to buy sufficiently powerful transmitters to hijack any radio station's signal. It's certainly not something your corner electronics store is probably going to stock. And the companies that do sell the more powerful transmitters probably want some kind of proof that you have a license to broadcast a signal.

On a small scale, maybe it should be alright, like hijacking only your own radio or broadcasting signals with a very small range for example. There's even a (legal) gadget called 'iTrip' I think which can broadcast FM signals.

 

[Danger]

On a small scale, maybe it should be alright, like hijacking only your own radio or broadcasting signals with a very small range for example. There's even a (legal) gadget called 'iTrip' I think which can broadcast FM signals.

There are a lot of 'wireless' devices that broadcast to FM receivers, generally using frequencies that a regular radio can pick up but that are not used commercially in the area. It's the same idea as a VCR or DVD player passing its signal to the TV on either 3 or 4, whichever is not broadcast within your reception range. Any non-licence ones can only go for a few hundred feet. Unless US laws have changed a lot, they're still the same as ours in that you need a radio operator license to use an RC aeroplane or boat, or to be a pilot. (The pilot licensing is separate from the need for a radio operator licence, since all ground-to-air communication exceeds non-licence wattage. I had to get the RO license before my first flight lesson, just so that I could legally communicate with ground control and the tower.)
If you try to 'hijack' a legal commercial station, you are looking at one serious world of hurt from the FCC. And it's a federal offense, not just a slap-on-the-wrist situation.

 

[Pengwuino]

You need a license to transmit over 200 feet i believe.

If you hijack a radio station, that's pretty much as serious as counterfeiting in the eyes of the US government when it comes to punishments and you will probably go to jail if you are caught. Depending on what you do, i think the punishment is up to 15 years.

 

[emotionalmachine]

They did it in Atlas Shrugged.

 

[Danger]

They did it in Atlas Shrugged.

And where are they now?