Intro: Modifying a Cheap Portable Cellphone Jammer
Specifically this model from dealextreme.com:
- Important Note: Usage and purchase of this item may not be allowed in certain countries. It is your responsibility to check for your local regulations.
Step 1: Dissasembly of the Jammer
In this step we will simply want to remove the top and bottom plates from the outer casing.
You will need:
- A small phillips head screwdriver
- a pair of pliers - optional
The first thing you're going to want to remove is the three antennas because the top plate will not come off properly with them attached. Next, there are four small screws which hold the top and bottom plates to the aluminum casing, remove these screws and then remove the on/off button from the side using the pliers or your fingers, pretty simple.
Make sure you don't lose the screws, put them aside with their respective cover piece.
Step 2: Removing the Inner Circuit Board and Locating the Adjustable Caps.
In this step we will remove the inner circuit board and locate the caps we will be adjusting.
Once the top and bottom plates are removed the inner board will slide out with some slight pressure. Once the boards out you just want to find the 6 small variable capacitors towards the middle of the board.
Step 3: Adjusting the Caps
In this step you just want to adjust each set of caps until you locate the correct band to block out whatever carrier or network you want to block.
in order to adjust the caps its best to use a small screwdriver, either a phillips head or a regular will do, you don't want to use allot of force here as the capacitors are very sensitive to force and could break.
If you have a frequency counter this step will be very easy as you can precisely tune your jammer, without a counter im afraid its pretty much guess and check. The easiest way I have found to do it is to call a number that continuously generates tones or some kind of audio
and then sit about 15 feet away and slowly turn the knobs until you hear the phone drop out
Here are some useful reference frequencies for tuning.
Cingular 1.850-1.865 Ghz 1.930-1.945 Ghz 1.730-1.735 Ghz 2.130-2.135 Ghz
Sprint 1.865-1.870 Ghz 1.945-1.950 Ghz 1.885-1.890 Ghz 1.965-1.970 Ghz
Tmobile 1.895-1.910 Ghz 1.975-1.990Ghz 1.710-1.720 Ghz 2.110-2.120 Ghz 1.740-1.745 Ghz 2.140-2.145 Ghz
Step 4: Reassemble
In this step you just want to reassemble everything. Start by sliding the board back in, then reattach the top and bottom plates with their respective screws (4 each) next remember to place the on/off button back in its socket, and then finally put the antennas back on ( make sure to put the correct antenna on the correct port).
After you have finished reassembling the unit you may find it annoying to continuously need to open the unit up and re-tune whenever you decide you want to block out a different carrier. In that case you can optionally drill out some small adjustment holes with a small 3/16 size drill bit. Make sure to disassemble and remove the circuit board fully before drilling!
Step 5: Have Fun, But Not Too Much!
Just remember, in most places actively blocking any kind of communications is illegal! so if you plan on using this device make sure you check your local laws and regulations.
Thanks to the guys over at PLA for the method, especially NAK (see you in class dude)