FM Jammer project

[Dannyx]

Originally Posted by momaka

Yeah, I thought about suggesting something like that too.

My original idea was get a butt-load of the cheapest Deer/L&C power supplies you can find, remove them from their case, and run a bunch of computers like that.... but that's probably too dangerous (though I will give you bonus points if you connect the BJTs on the primary heatsink through long wires wrapped around the AC input. )

But yes, relay coils from appliances produce a crap-ton of noise - even more than a cheap Deer PSU without any filtering. Just make 20 of those devices and put them everywhere in the building. Then no one would be watching TV or listening to music, because even if that doesn't screw up the reception, the speaker popping noises one would hear on their TV or radio will drive them insane.


It's not hard at all, but you do need some equipment.

If you are serious about learning and building electronics, you should invest in a good multimeter with more functions, like capacitance, frequency, PWM, AC current, as well as Mix/Max and Rel. functions. The cheap transistors testers on eBay and elsewhere online are also quite useful - they will provide you with capacitance, inductance, and cap ESR measurement, which can come in very handy when re-using components.

The relay idea sounds right up my alley, though again, I reckon the range of such a contraption would be pretty limited....perhaps up the voltage to a 220v relay ? *wink wink*

[stj]

no, but maybe adding an "antenna wire" to one end of the coil would help.

[momaka]

Could even use a regular TV antenna. Remember what makes a good receiving antenna usually also makes a good broadcasting antenna.

[japlytic]

On a related subject, how about a TV station jammer?

[WarHawk8080]

Raspberry Pi can output FM modulation on one of its IO pins, then all you need is a Low Noise Amp and done deal
http://www.makeuseof.com/tag/broadca...-raspberry-pi/

Biggest thing is...if you broadcast on a FCC licensed frequency...and become a nuisance...they will come find you...

If you want to filter FM...try this
https://oshpark.com/shared_projects/SSrRYkXY

[Andyy]

Originally Posted by Dannyx

I'm aware of that, but being realistic, there's no real way for someone to find out why their radio suddenly only plays static...nobody would bother and would just blame it on poor reception, the weather or just switch to something digital way before that IMO.

If it's FM radio and you're broadcasting just a carrier with no modulation, you'll actually mute the radio....not cause static.

[jondoe]

I've been playing with a KT0803L based Arduino FM module, if you crank the RF gain right up and cut an antenna to the exact length of the frequency you can push 1/2 to 3/4 of mile range in a mildly built up area. Not bad for the money!

[Dannyx]

I just remembered I once made an accidental discovery, I think it was in my early teens, which is somewhat along the lines of what we're discussing here: I cut a piece of copper board into a disc and attached it onto the spindle of a hard drive with the intent of placing LEDs radially on it and have a bit of a light show/POV thing going on...anyway doesn't really matter.

I had just one LED in place on the board and fashioned some crude brushes out of stranded wire so I could power the LED while the disc was spinning. The thing was going at 7200RPM, it was well balanced and worked exactly as I imagined it and when I touched the brushes to the tracks I cut into the board, the LED did come on as it was supposed to, but at the same time I noticed the radio I had going in the room cut out. Took the brushes off, the radio came back in. Touched them to the spinning platter again and there was static again. I believe my contraption had the unintentional side effect of acting like a spark gap ? Just an uneducated guess...though I doubt it'd be too effective over large distances AND though concrete walls, I still find it interesting.

[Dannyx]

Oh yeah guys, just in case someone is still watching this thread after all these years, I'm now having the same issue at work where we just can't settle on a single radio station and some of us insist of treating everybody around here like sh!t and act as it's their shop and think it's their way or else, so it's f***ers like these who are just BEGGING to get jammed like this to be made an example of Best part is the radio is close by, like 2-3 meters if that, so I'll definitely look into something like THIS, since it's got some nice parts there which I can easily find and also seems to be the standard circuit for something like this and all sources show this one, more or less.

Tired of hearing the same songs every 10 minutes.....>_>

[sam_sam_sam]

Is this what happens when you get piss off and you have free time on your hands

I find this post very amusing and at times very funny

I once had bought one those FM transmitters and it worked very well as long as you had enough space in between stations

[Dannyx]

Originally Posted by sam_sam_sam

Is this what happens when you get piss off and have free time

Yes, that's what happens when you're driven mad because you can't focus on your work because of all the noise.....yeah, that's just me. Some people can focus even when there's an army of tanks passing by, but I much prefer silence.....I can be a weird SOB myself sometimes and get people to hate me, I know...

Originally Posted by sam_sam_sam

I find this post very amusing and at times very funny

I always say my purpose in life is to make people laugh and having said that, I'm pleased to see I'm succeeding

Originally Posted by sam_sam_sam

I once had bought those FM transmitters an it very well as long as you had enough space in between stations

On a more serious note, if you're referring to those cigarette-socket style FM broadcasters you use to "upgrade" a non-USB/BT/AUX capable headunit, I too was thinking of going with one of those, since it would enable me to actually inject something over the hijacked frequency, instead of cutting it off entirely, which would give away the trick. This way, I could keep the radio working and the guy will think that's just what's being broadcast....it will take a while before he figures it out Even though it's a fairly common thing, I can't locate one right now or someone who has one to try it out for me, since I'd be using it in the opposite way it was designed: on top an existing frequency, instead of an unused one. The more powerful station will likely overpower the little transmitter and I'll end up with a garbled mess for sure...unless I open it up to hack it somehow to make it more powerful, if at all possible....

[sam_sam_sam]

No I talking a Ramsey kit that you put together I am talking about what you could find years ago

They do not sell this kit any more at least the last time I was on there site and that quite a few years ago go

[Dannyx]

Apparently a RaspberryPi can function as a jammer too. I don't have one, though it would be tempting to get one just for this purpose Makes me wonder what other device has the ability to replicate the device in the project....I don't know much about specific microcontrollers and what they can do, like why the Pi is capable of doing it, for instance. I'm guessing the max frequency at which the microcontroller can operate is a factor, also available memory (?)

[stj]

in theory you could build a frequency hopping transmitter that sends out your music across the entire frequency range of the radio!

[Dannyx]

Really like this one, though it's the same idea as before, just slightly more advanced. If it could also play audio play files off a USB thumb drive, that alone would make me want to buy a PI right now I don't know sh!t about Pi, so this would be a learning experience too I'm always up for learning something new

[sam_sam_sam]

I stand corrected they still have them

https://www.aircraftspruce.com/catal...YaAqPxEALw_wcB

[momaka]

Originally Posted by Dannyx

On a more serious note, if you're referring to those cigarette-socket style FM broadcasters you use to "upgrade" a non-USB/BT/AUX capable headunit, I too was thinking of going with one of those, since it would enable me to actually inject something over the hijacked frequency, instead of cutting it off entirely, which would give away the trick. This way, I could keep the radio working and the guy will think that's just what's being broadcast....it will take a while before he figures it out Even though it's a fairly common thing, I can't locate one right now or someone who has one to try it out for me, since I'd be using it in the opposite way it was designed: on top an existing frequency, instead of an unused one. The more powerful station will likely overpower the little transmitter and I'll end up with a garbled mess for sure...unless I open it up to hack it somehow to make it more powerful, if at all possible....

That's what I'd try first.

I bought one of those cigarette lighter plug FM broadcasters some years back. Originally, the thing barely had enough broadcasting power to be caught by my car's radio, even on an unused -even- frequency number (here in the US, we don't use even number frequencies for FM radio - only odd numbers.) So I opened mine up and soldered a 30 cm / 1ft copper wire for an antenna. That boosted the transmitting power many times over. I could now set it to any frequency I wanted, and my car's head unit would catch it - even over stations with strong broadcast. Next, I stripped the end of the antenna I soldered and added several jumper wires to act as an even longer antenna. With that, I can have the little FM transmitter even 10-15 meters away and still get perfect reception.

It's worth noting that what I did is probably illegal, as I'm sure that FM transmitter is no longer FCC part 15 compliant. On top of that, those FM transmitters tend to have absolute garbage frequency locking - you might find that you're broadcasting not only on the frequency you set it to, but also on a few other "random" ones. At least that was the case with mine - found it broadcasting on several non-adjacent FM stations, lol. Of course, I didn't really use that thing that much - only occasionally on my long commutes from college to home, where most of the time I was on a highway far away from cities, so not much to disrupt with my "noisy" FM transmitter. Mostly I got that thing just for fun / to experiment with.

That said, another thing worth noting about those FM transmitters is that their transmitted sound quality is usually not that good - particularly with music with heavy bass. Also much more quiet. And depending on the receiver, it may only pick up the signal as Mono broadcast vs. Stereo. But if you want a quick-n-dirty way to try to jam your colleague's radio, I think this would be it. Bonus points if you make your own playlist and also record some random advertisement/portions from the radio frequency that your colleague listens to. Then just mix that with the music tracks and watch him get really confused about their radio station. Imagine playing some Metallica or Dubstep on a classic music radio station... or vice-versa.

[TechGeek]

Build a decent FM transmitter, then blast Tourette's Guy over the frequency.

[eccerr0r]

I think a lot of the FM transmitters out there are pretty crappy in terms of frequency lock. A lot will drift and drift badly. I currently have three FM transmitters:

one is a little box with an antenna. VERY bad temperature drift. Tune with a screwdriver (warning sign #1) and does not go the whole range.

second one is a "Jupiter Jack". Has few fixed frequencies. Did not like as it was mono and audio frequency limited. I didn't test fully.

Third one is part of a MP3/microSD player. This one actually seems to lock on frequency much better, and also can tune the whole 3 meter range. It also has A2DP bluetooth personality, and sounds fairly good. I stopped using its bluetooth and eventually whole thing because its behavior during car starts and stops, pairing resync took forever.

IMHO if you don't have a crystal controlled transmitter, don't bother, unless you were planning on simply annoying versus playing your desired music. The drift is awful unless you can keep the transmitter at a constant temperature somehow.

[Dannyx]

Our buddy here uses a small boombox on his desk with a tuning dial - not digital. Not exactly hi-fi, so quality is not all that important in the long run. If anything, even if I get my transmitter to mess up the existing transmission, without my tunes coming in perfectly clear, it should still be enough to make him touch the tuning dial....at which point I'll retune my jammer as well and keep going He'll undoubtedly get tired of it eventually and probably upgrade to a better radio with a digital tuner, at which point I'm not sure how well my transmitter will perform still....guess I'll get one and try it out.

I wonder how much the price point plays a role...I'm guessing not too much, because they all have to comply with certain limitations, so the price may only add features and not overall power, so I guess for this purpose cheaper is better...