posted on Apr, 22 2005 @ 11:30 PM
Stealth? Yes and no.
I'll try to answer your question without going too deep. Radar works by sending out RF energy as waves. These waves bounce off solid objects and
return the the radar receiver, where they are measured. Radar travels at the speed of light, so by timing the return you can calculate the range to
the object. Some radars use the Doppler effect to measure the speed of an object. The Doppler effect causes waves from an object approaching you to
appear to have a higher frequency and waves from an object traveling away from you to have a lower frequency. The horn of an approaching train is the
classic example for Doppler shift. The radar has a transmitter and a receiver, and the two share time to create what's called a duty cycle. A radar
may spend x amount of time transmitting, then 3x amount of time receiving, or 'listening' to see if it gets a return from the signal it transmitted.
This would give a 25% duty cycle.
If you are able to transmit your own RF energy waves into a radar receiver you can fool it into thinking it has received a return different from you,
or you can overwhelm it. If you know the frequency a radar operates at, you can simply blast a high power continuous signal of that frequency at the
radar. This signal will overwhelm the radar because the radar will receive one constant return for the entire 'listen' phase of it's duty cycle.
Since you are transmitting at a higher power than the radar is receiving it's own transmissions the jammer 'drowns out' the real radar return.
Some jammers will send echos, or multiple fast returns of about the same power and frequency of a normal radar return. This will cause the radar to
think it is receiving returns from multiple objects when in fact there is only one.
Other jammers will distort the signal from the radar by increasing or decreasing the frequency of the return to give false speeds or other
Back in the day a lot of early radars didn't have overload prtection circuitry so a jammer that was of sufficient power could actually fry a radar
receiver and cause it to catch fire, like lightning destroying a TV set.
So there is a Stealth effect in the fact that the radar will not see the jammer, but it will know that there is something somewhere along that
bearring that is jamming. It won't know the range to the jammer and therefore will not be able to track it.
There are a lot of ways to counter jamming as well. Many modern radars actually encode encrypted counters into the radar transmission. This way it
can tell the difference between it's own transmission and the one from the jammer. Some radars use frequency hopping, where it uses several
different frequencies to transmit at. It knows the order of the different frequencies it sent out, so it knows which ones to listen too. The jammer
in this case would have to identify all the frenquencies used by the radar and figure up the frequency of use of each, then jam at those frequencies.
This makes the jamming much less effective. Some radars will use both methods, encoding and frequency hopping. This seriously reduces the effects of
Some radars have a burnthrough mode, where the full power of the radar is used to overpower the jammer and receive returns. Here's a good example.
You're in a dark room and someone turns on a maglight and shines it in your face. Suddenly you can't see anything but the maglight. You know
someone is there but you can't see them. If you pull out a million candle power spotligt and shine it back at them, you will be able to see them.
When you light off a jammer it is only effective to hide objects in your immediate area, basically directly in front of you or directly behind you.
An aircraft could fire a missile and assuming he had an effective jammer, he could jam the radar so the missile wasn't detected. An aircraft can jam
an incoming missile so the missile can no longer track the aircraft.
Electronic warfare and electronic countermeasures are a really cool part of modern warfare. Each of the branches of the military have personnel
specially trained for EW, ECM, and ECCM.