FM frequency jammers

[channel1]

Just a quick note:
You don't exactly want to jam a particular frequency, you want to disable a radio, that is presumably in a fixed location and quite close.

Instead of transmitting over the commercial broadcast frequency, it would be more effective, and less likely to cause spill-over problems, if you went after the IF frequency. With a highly directional antenna, you would be able to target the radio, and there shouldn't be any problem with spill-over to other devices.

Of course, it might be easier just to call up the radio station and put in requests for what you want to hear. :)

-rcv-

[Zath]

Where is the antenna for this troublesome radio located? Is it in some place you can physically reach? You might be able to disrupt signal reception with a grounded metal waste basket or some home made concoction and a bit of aluminum foil. More exotic alloys may be required for full protection however. Perhaps you should try passing a $20 bill to the tech guy first. Alternatively, you can wear this to work and see if the people up in the main office will take notice :lol:

[kandrathe]

If I were young, fearless and immortal, here is where I would start.

To Design and Build a Portable, Miniaturised, Multichannel FM Transmitter

With the side benefit of learning by doing it. Just remember to keep the power low enough to get the job done, without alerting the authorities and ending up paying a huge fine. And, yes, there are people who drive around with radio detection equipment that can triangulate on your position based on angle and power emitted. Many RC cars, garage door openers, and etc., use an FM radio frequency outside (below IRCC) the commercial broadcast range. A good test would be to see if you can hear your broadcast from the street. If so, your generating too much power output. Also, if you broadcast at exactly the same frequency, what you will most liklely hear is both your transmission and the other combined. You could try varying your frequency to just above or below to try to force the offending receiver to lock onto your frequency instead.

You might want to read up on the laws you might be violating though, just in case. It's good to know what the penalties might be in advance so it is not such a shock when they sentence you to death (under the Patriot Act, of course. :D)

[TriggerHappy]

Thanks muchly!

Already started deciphering those instructions, should only take me a few weeks :blink: . Thankfully my father is an electrician with a good understanding of electronics as well, he's willing to help me out.

I'm pretty sure the laws here in Ontario, Canada are similar to the FCC laws in the states, but then i only need a few meters in diameters to reach the radio. I hope such a short ranged signal won't be detected. Are there many of these detectors driving around between 11pm and 7 am at night :D ?

[--Pete]

Hi,

But from my days playing with radio, I seem to remember that a signal below some power level is not controlled by the FCC. I suspect the Canadian equivalent has the same type laws, or any user of a power drill might face charges :)

Since the strength of a signal drops off pretty fast (almost like the inverse square, depending on broadcast antenna geometry), if your transmitter is a lot closer than the one you're trying to override, it can be a lot weaker. Possibly weak enough to keep you legal :)

--Pete

[TriggerHappy]

Since the strength of a signal drops off pretty fast (almost like the inverse square, depending on broadcast antenna geometry), if your transmitter is a lot closer than the one you're trying to override, it can be a lot weaker.  Possibly weak enough to keep you legal :)

And, i'm hoping, weak enough not to cost me an arm and a leg in parts.

I already talked to my employers about the idea and they will chip in, so i can go higher on the parts cost, if necessary, than i could afford alone.
If only there were other things that annoyed my employers as much as they do me, that they wanted to spend money on :lol: .

[kandrathe]

If only there were other things that annoyed my employers as much as they do me, that they wanted to spend money on  .

Like underpaid overly intelligent night shift workers?

[TriggerHappy]

I've recently recieved a PM from a person intersted in this subject. Since I did find a solution, I'll post a copy of my reply here, just incase anyone else is interested.

I saw your post on jamming a radio within a few meters. Did you have any success? I have been searching for a solution to the same issue though a different senario applies. I havn't found anything for months. Are you willing to share the plans that you have? I would greatly appreciate it.

Thanks

Actually yes, I have found the perfect solution for this, just never bothered to post it up.

This is the device I ended up using:

http://www.mp3kit.com/Products/PLL-1_FM/...udiax.html

It successfully overrode an FM radio signal from a radio 10 meters away. I simply set it to the station I wanted to override, but not transmit anything, and the speakers would silence :D.
However my transmitter wasn't powerful enough to actually be able to play my own music. I mean I could, but the quality wasn't great at all. For that, one would need a non-occupied station.
But, my main purpose was achieved, so I was happy.

The only problem was with the use of AAA batteries. The unit can't be powered by a DC adapter.

However there are other "FM transmitters" that are more powerful, and will be able to override the signal so well that you could play your own music even while overriding an existing radio station. They're abit more costly though.
Some of these are capable of being powered by a DC adapter. Google for "FM transmitter" instead of "FM Jammer". That was my initial mistake, and the reason I couldn't find anything at the time of my thread :).

Hope this helps.