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Active EPM measures are detectable by the enemy; such as altering transmitter parameters (e.g. frequency or PRF to ensure continues, effective use of the EM Spectrum).

Passive EMP are undetectable measures such as changes to operating procedures, signal processing options or technical features of the equipment which are meant to ensure continues, effective friendly use of the EM spectrum.








Continuous Sine Wave Jamming otherwise known as black jamming, is where a powerful concentrated single frequency Sine Wave is transmitted at the same frequency as the enemy's RADAR echoes. This will reduce the sensitivity of the enemy's RADAR causing a blank sector on their PPI. If enough power enters their RADAR causing a blank secetor on their PPI. If enough power enters their RADAR antenna side lobes, it is possible to blank out their whole display. This is why it is called "black jamming".