Barrage noise jammers (to which you refer) have always been the most difficult jammers to deal with in the sensor. The usual countermeasure to them is "region

Barrage noise jammers (to which you refer) have always been the most difficult jammers to deal with in the sensor. The usual countermeasure to them is "region blanking", where the sensor simply stops listening for returns on the azimuth of the jammer. Fortunately, barrage noise jammers are the easiest to deal with using AGM-88 HARMs. Edit: Also, I should note that barrage noise jammers have limited bandwidth, and have to trade off bandwidth for power. If the APCN system keeps its operating frequency sufficiently masked it may require multiple jammers to actually interfere with the system sufficiently.