Eli5:Whats the science behind radio jamming and what does that have to do with frequencies ?
In: Physics
/u/HatsAreEssential gave a quite correct general answer.
An exception is a technology like Code Division Multiple Access (CDMA). There are various CDMA implementations. It was originally conceived by actress Hedy Lamarr during WWII. In that version, the radio frequency used is constantly jumping around, making it difficult to jam. More modern versions sort of use a very broad band of radio spectrum but only pay attention to different parts at a time.
Both of these are more difficult to jam unless your adversary is willing to forgo using radio themselves and has equipment powerful enough to spread noise across a lot of the radio spectrum.
When you have an antenna it sends the radio receiver the sum of all the radio energy it absorbs. Just like how a microphone sends the sum of the sounds from all the musical instruments in an orchestra to a recording device.
The radio contains a tuner, which rejects all the frequencies besides the “station” you are tuned to. This is how one antenna works with all FM radio stations.
However, a jammer transmits at the same frequency as the signal it wants to corrupt. The antenna adds this jamming signal to the other things it receives, and the tuner isn’t able to reject it by frequency, so it turns the signal into worthless noise.
To return to the orchestra analogy, you might be able to selective listen to the trumpet by tuning out the higher-than-a-trumpet and lower-than-a-trumpet notes, but if someone in the audience blows a buggle that has the same sound as the trumpets, you get garbage.
Radio works over narrow frequency channels. Typically only one device can broadcast at a time, otherwise the 2 communications come out garbled. One way to jam these is to broadcast static and noise over that channel to disrupt any valid transmissions. Imagine two people trying to talk, and you walk up to them with a boom box blasting dubstep at max volume. The valid communication becomes impossible.
Radio waves are like sound waves. If you have two people talking, and you make a really loud sound, they cant hear each other because they only hear the loud sounds. Now if you make noise on a radio frequency, you can make both sides just hear noise (static) and you have blocked communication.
If you know the frequency of the receiving radio you can tune your jammer to that frequency and dump a bunch of power to raise the noise level above the “signal” ratio.
This will either cause the receiving radio to not hear anything at all or hear music or noise.
In the case of GPS jamming they put noise on the same frequency that your GPS receivers use. This causes you to lose connection to the weak satellites and effects what ever gps device your using from not working. Everything from credit card readers to your navigation uses GPS.
A couple points to remember. You can’t “jam” a jammer. You can crank the power up higher of the transmitting radio to overcome the jammer or you have to physically turn the jammer off either with bombs in war time or in the case of protected radio frequencies , by getting the government involved.
In real life it’s harder to jam things because most radios will ignore the jamming signal because the modulation, encryption or the squelch doesn’t match. If the jamming signal is wide and powerful enough it will just cause the radios to go silent.
But this takes a lot of energy and these are easy to identify and locate.
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