DIY Culture

My Cell Phone Jammer

Many months I was looking for a good instructions on how electronics fan like me can make a simple cell phone jammer. There were many tries and fails, but recently I came upon the blog of Jammer Store Inc. where their tech guys explained now their work must be done.

Their post opened my eyes and made this hard task a little bit easier to understand and implement. So finally my first mobile phone jammer appeared. And now you may also make one for yourself.


Circuit Board from top

Technical Details

I have selected sweeping oscillator to be my jammer's VCO because it is very effective. It can be hard to construct if you are the beginner in electronics, but with nice testing equipment for radio frequencies all will be fine. Most cell phones use 800MHz frequency so VCO is tuned to the same one.

As your noise source of the jammer you can take 45MHz clock oscillator that goes to local oscillator port which is located at the circuit mixer. Local oscillator signal is going through impedance matching network and this action equates impedance of this clock oscillator with the circuit mixer port.

RF input (the circuit mixer port) and RF output are connected to the 800MHz antenna and circuit amplifier respectively. The amplifier is there to increase output power for another 15-16dbm and then amplified signal is giong to another 800MHz antenna.


Circuit Board

How This Device Works

GSM800 is the most popular band for cell phones. Such cell phones have their transmitted frequency always separated exactly by 45MHz from its received frequency. So when the call attempt is made it jams itself via returning signal. Its own signal! It must be fun to make some annoying phone talker to stop in this way.

This cell phone jammer may also be used to block signals of cell-based car trackers and even mobile phone controlled IEDs. Who knows when this may be handy?


Case and Connectors

Pics And Notes

The mixer is originally made for 600MHz but was reconfigured for new parameters.

RF amplifier makes outgoing signal really more powerful and effective for the price of additional power supply.

UHF connectors are the device's input and output channels along with antennas. Whole jammer is contained in the aluminium box (old but reliable).

UHF connectors are attached to the circuit board.


Cell Phone Jammer Inside

Nine volts battery is a power source. Voltage regulator bein used to match voltage. The battery is placed inside the box as it is shown at the picture (it is separated by the foam plastic, just in case).

The power switch is a must for the device to control it properly. The antennas connected to the UHF connectors to receive cell phone signal and transmit jammer signal.

There is a schematic at the bottom line.

I guess that's all. Now you can try to do your unique model :)

BearGrills 15:13, June 30, 2011 (UTC)



Jammer Scheme