Table Of Contents
Principles of Jamming
The principle of a jammer is to generate a radio signal at a higher power than the radio signal you are trying to jam or block. For example, if a device is emitting a radio signal at 100MHz, then all you need to do is emit a strong signal at 100MHz near the receiver. Since the receiver will receive your stronger jamming signal in preference to the weaker genuine signal, you will have blocked the receivers ability to receive that broadcast.
It's worth noting that the jammer does not disable the genuine transmitter in any way. It merely prevents the receiver from getting the genuine signal. Therefore other receivers far away from the jammer can still pick up the genuine signal.
If you look at the diagram above, you'll see the genuine transmitter device T. Both R1 and R2 are in range of the genuine transmitter T. However, if a jammer device is activated at J, then R1 will receive the signal from T, and R2 will receive the signal from J. This is because the signal from J is stronger than that of T for R2, mainly due to how close J is to R2.
Mobile Phone Jammers
Mobile Phone Jammers are designed to generate radio signals in all the bands used by mobile phones. This renders a mobile phone, that's close to a jammer, completely useless. Effectively the mobile phone cannot completely establish a connection with the mobile network, and so cannot receive or make calls. In some cases, the mobile phone cannot see a network at all, so even text messages are affected.
The common mobile phone frequencies are below. You'll notice that the mobile phone network uses a large range of frequencies for each band. Therefore a mobile phone jamming device will use electronic circuitry that shifts the output radio frequency through the whole band to knock out anything using that range of frequencies. For example, on the GSM900 band, the jammer will start at 880MHz and work its way up to 915MHz in 500kHz steps every 0.1 seconds. Therefore the whole of the GSM900 is covered in a few seconds.
- GSM850 = 824 - 849 MHz paired with 869 - 894 MHz
- GSM900 = 880 - 915 MHz paired with 925 - 960 MHz
- GSM1800 = 1710 - 1785 MHz paired with 1805 - 1880 MHz
- GSM1900 = 1850 - 1910 MHz paired with 1930 - 1990 MHz
If you want to look at a range of jammer products, take a look at JammerJammer.com. But do bear in mind the legalities of owning a jammer too.
Other Jammers
You can design a jammer to knock out virtually any radio signal. However, if you have the money and skills to do so is another matter. Even a mobile phone jammer is a complex design, as shown by the Wave Bubble portable RF jammer design.
However, you can buy jammers that operate on 2.4GHz that block wireless computer networks, Bluetooth signals, wireless video senders and wireless spy cameras. Even a spy camera or wireless network running at a higher power than a neighbouring device can serve as a crude jamming device.
Legalities of Jammers
When it comes to jammers, the legal side of things is much clearer. It is illegal to own or operate a jamming device. This is because the chance of knocking out important radio signals for emergency services, airports, marine craft and government agencies is very high.
