radiated power), the radars ERP and required J/S (for the jamming to be effective). Inadvertent jamming In some cases, jamming of either type may be caused by friendly sources. Inadvertent mechanical jamming is fairly common because it is indiscriminate and affects any nearby radars, hostile or not. Electronic jamming can also be inadvertently caused by friendly sources, usually powerful EW platforms operating within range of the affected radar. Countermeasures Constantly alternating the frequency that the radar operates on (frequency agility) over a spread-spectrum will limit the effectiveness of most jamming, making it easier to read through it. Modern jammers can track a predictable frequency change, so the more random the frequency change, the more likely it is to counter the jammer. Cloaking the outgoing signal with random noise makes it more difficult for a jammer to figure out the frequency that a radar is operating on. Limiting unsecure radio communication concerning the jamming and its effectiveness is also important. The jammer could be listening, and if they know that a certain technique is effective, they could direct more jamming assets to employ this method. The most important method to counter radar jammers is operator training. Any system can be fooled with a jamming signal but a properly trained operator pays attention to the raw video signal and can detect abnormal patterns on the radar screen. The best indicator of jamming effectiveness to the jammer is countermeasures taken by the operator. The jammer does not know if their jamming is effective before operator starts changing radar transmission settings. Using EW countermeasures will give away radar capabilities thus on peacetime operations most military radars are used on fixed frequencies, at minimal power levels and with blocked Tx sectors toward possible listeners (country borders). Mobile fire control radars are usually kept passive when military operations are not ongoing to keep radar locations secret. Active electronically scanned array (AESA) radars are innately harder to jam and can operate in low probability of intercept (LPI) modes to reduce the chance that the radar is detected. A quantum radar system would automatically detect attempts at deceptive jamming, which might otherwise go unnoticed. Anti-radiation missile (ARM) also known as Home-On-Jam (HOJ) missiles: When a target is using self-protective jamming (SPJ), it essentially broadcasts its position. An ARM could be deployed and take out the jamming source. The missile utilizes passive RF homing which reduces its probability of