Cellular phone jammers are generally considered illegal by the FCC, as it effects the communications of emergency personnel who use the same frequency as cell phones for much of their communications, as well as using cell phones themselves. However, prisons, schools and city governments have campaigned to allow use of jammers to keep people from cheating in class, to keep cabbies and limo drivers concentrated on the road and to restrict prisoners from using smuggled cell phones.
Wave Bubble Cell Phone Jammers
As cell phone jammers are illegal, they must either be ordered illegally from overseas or built illegally at home. You need some real skills at working with chips and antennae. The Wave Bubble Jammer, in particular, jams all types of radio frequencies beyond cell phones. A lithium-ion battery must be installed to provide power and can provide up to two to four hours of jamming, depending on which frequencies are in its vicinity. The battery is rechargeable via a USB connector or a common 4 mm DC jack. You can also use AAA batteries.
There are two antennae which run out of the microchips in the jammer which pick up a variety of frequencies within a twenty to twenty-five foot radius. There is a large amount of difficult SMT soldering that must be done to install the specific chips to make this work, namely multiple TSSOP and SOT chips, 0603 RC's, along with obscure parts, and equipment necessary to properly construct and debug the device. The sources for what these are specifically are not available due to the fact that this device is illegal within the United States.
Cell Phones Modified to Jammers
Some cell phone jammers have been modified from old cell phones to be on the same frequency as the cell phone and emit a tone that makes it impossible to hold a conversation on the phone. Again, these are also illegal and difficult to build yourself, unless you have some knowledge and skill at soldering microchips and manipulating radio frequencies. Police CB radios work in the same way as these cell phone jammers, buy picking up all frequencies in their vicinity so that they can be heard over the CB. The cell phone jammers go one step further to block transmissions.