Low voltage "jamming" for practical jokes

[MarcusFunt]

Hi all.

I want to create a simple, cheap RF wifi jamming board for doing practical jokes on my mates. I found the attached schematic online and wake to ask some questions.

What modifications would be required for it to work at a lower voltage(preferably a 3v coincell).

The crystal is only rated for a fairly low frequency. Will the circuit even work?

Can I directly attach an antenna to the output of the circuit to transmit RF??

The range should only be 20-120cm, to not get in trouble. How do I change the power?

I would like for L1 to just be a simple smd inductor. What value and power should it be??


Any assistance would be greatly appreciated.
Thanks!

[PA0PBZ]

This will not do that! It will produce a signal every 96.015 MHz and none of the harmonics will even fall inside the 2.4 GHz WiFi band.

[MarcusFunt]

What if I change the crystal to a 24 or 240 MHz one?

[PA0PBZ]

The WiFi band is (depending on the region) 60MHz broad, you need a different technique to block that. No, I'm not going to tell you how, but you'd need a lot more power than a coin battery could provide.

[p.larner]

look for uhf spark transmiter schematic,or better stil disable your microwave oven interlocks and fire it up with the door fully open,then see if you can get nominated for a darwin award.

[rhodges]

If you want a prank, how about programming an ESP32 to send insulting messages as the SSID?

[Wallace Gasiewicz]

Link to WiFi Jammers:
https://www.wxyz.com/news/oakland-county-sheriff-to-announce-new-regional-task-force-to-combat-break-ins

[coppercone2]

this is a terrible idea

[Kim Christensen]

Instead of jamming the WiFi, why don't you make a device that intermittently resets or power cycles their WiFi router instead. That would be a lot easier and wouldn't interfere with neighbors or get you in trouble with the local authorities.

[Whales]

Modern consumer radio protocols (such as those in the many wifi standards) are designed to handle relatively large amounts of interference.  They have to be this way because different people using them naturally interfere with each other, and you can't sell a product where only one person in a neighbourhood can use it at a time.

There are other Denial Of Service (DOS) attacks against wifi that require only a laptop and won't interfere with the reception of neighbours.  Whether or not they will work on your friend is complicated as there are many different versions of wifi and basestation/client implementations with different flaws.  Such DOS attacks are considered security flaws, so if you want to find out more then the best information will be available in linux wireless & security communities.

[radiolistener]

I think your circuit won't works for wifi.

[Simon]

Radio jamming is not really a very good idea. There is electronics, and then there is this mythical thing few understand well enough called RF where if you have not figured already that electronics is simply a programming language for physics, with RF you will learn maybe the hard way that is is the essence of physics. If you have to ask, just don't try it.

In my last job I had to roam the shop floor and measure stuff. Tired of being caught in the cross fire of the different radio stations people played at high volume in order to drown out the next persons radio I hatched a plan. I bought one of those FM transmitters that were popular to plug into MP3 players etc to be used in your car to add modern sources to your old radio. All I had to do was tune it to what they were tuned to and the blank signal would drown out the station and mute the radio.

I then had quite a bit of fun with one of the welders, he wanted to listen to BBC radio 2, like all BBC stations this is transmitted on 2-4 frequencies at a time, if you are at a point where you can pick up from multiple transmitters you can often get it good twice or more. So this bloke got up and retuned his radio, so I retuned my transmitter, and he retuned his radio, after a few goes ho just turned it off.

I had all this fun with an off the shelf item that was legal.

As wifi has a protocol to stop collisions it will be harder to coerce existing hardware to do this.

[Andy Chee]

I bought one of those FM transmitters that were popular to plug into MP3 players etc to be used in your car to add modern sources to your old radio.

I wanted to do a similar thing on multiple stations, using a muticast transmitter like those used for emergency broadcast in underground road tunnels (i.e. announcements break-in to your radio, regardless of station).

Unfortunately they appear to be less readily available on eBay!

[TC]

In the USA jamming isn't a joke. It is illegal.

[wasedadoc]

The circuit as drawn in the schematic of the opening post doesn't even apply any power to the oscillator.

[Lambda_]

In the USA jamming isn't a joke. It is illegal.

why not both...

@MarcusFunt
Wifi is 2,4/5ghz
And not easily to jamme.

If you want to do something like this get Cheap ESP8266 boards.
Serch for " raw socket"
they can send and overload networks by spamming arp requests or sending deauth packages 
https://github.com/SpacehuhnTech/esp8266_deauther

[djacobow]

In the US, jamming is illegal but enforcement is joke. The FCC has pretty much thrown in the towel on investigating reports of interference. Unless the interference is widespread, consistent, and, most importantly, pisses off a paying licensee, you can do whatever you want. In this case, since WiFi is in the ISM band, their likelihood of giving any forks is essentially zero.

That is the sad fact.

[Wallace Gasiewicz]

Years ago someone built a jammer for police speed radar.  It would insure you were going the speed limit, You set the speed.  Someone built one and left it on while going home in his subdivision.  He got a big surprise, there was a cop who gave him a ticket because his radar said the fellow was going 70 MPH!!   

The cop gave him the benefit of the doubt and only ticked him for far less speed, but he did get a ticket!!!   

True Story.

[radiolistener]

I tried to play with ADF4351, tune it to wifi channel and connected output to wifi antenna, but wifi still works 
It stops to work when I put generator antenna close to tablet and make a little frequency offset, at some offset it stops to work, but it still able to receive other wifi channels. I tried to do frequency sweep to cover entire channel bandwidth 50-1000 times per second, but it don't works, wifi works ok.

ADF4351 has about 0 dBm output (0.001 Watt), I believe it can works better with 2-4 Watts power amplifier, it can just overload nearby wifi receivers, but it requires precise tuning on specific frequency. With using circuit posted on first topic starter post it is almost impossible.

There are at least two issues with topic starter circuit:
1) no way to tune at specific frequency of wifi channel
2) too small output power

And it seems that constant carrier is not reliable way to jam wifi channel, there is needs for a more smart patterns.

And there are at least two common WiFi bands - 2.4 GHz and 5 GHz. So, even if you jam 2.4 GHz, 5 GHz still can work...

[DavidAlfa]

There're some jerks at work spending half of their working time looking at the phone (Football matches, bets, Tiktok crap..).
As a personal scientific research, would love to jam their 4G signal and see what the animal does when he's forced to work.
No shame, I have to make my job, and then part of their's!

[radiolistener]

You can try to jam 2.4 GHz WiFi with old microwave oven, just power on magnetron with opened door and direct it to WiFi receiver. Microwave oven works at 2.4 GHz band and has pretty high power to completely overload WiFi receivers for all channels... I think it also probably can affect 5 GHz band, because receiver don't have good enough filter, because it needs to receive 2.4 GHz...

If WiFi receiver will be too close to microwave oven, it's receiver can be burned out.

PS: be very careful with microwave oven experiments, it has high voltage and high power emission, so this can cause serious burns if parts of your body will be on too close distance or can leads to death due to high voltage

Here is video with some microwave oven experiments:

[Whales]

Please don't do that stuff with microwave ovens.  They output dangerous quantities of RF if you run them exposed (enough to cause blindness and burns).

[DavidAlfa]

Ahh the Kresoan people, sadly they will die young.

[coppercone2]

they may actually vastly increase their chances of survival by having a wireless jammer, being in Ukraine, if used responsibility, whatever that might be, no idea actually, scary stuff. that seems like mosquito spray in the jurassic era

[DavidAlfa]

But their "magnificient" magnetron jammer is crap, close to the free energy videos level, well, like most of their videos, lots of these people seem to have some mental issues and strange behaviour.

A simple cone antenna can only do so much, so the range was very short, so short that you would need to enter the facilities to cause any effect, at that point, in the one in a million chance enemy didn't see you and consequently shot/nad'ed/shell'ed, you could simply destroy the equipment with a hammer, saving all the effort .

Perhabs with a more sotisficated high gain directional design, so the power concentrates on a very sharp beam.