Cover pulse jamming is deception with a concealing purpose: instead of pulling the track away, the real echo is buried. At (and around) the moment the real echo reaches the radar, the jammer transmits a wider, stronger pulse — noise or DRFM copies — that completely covers the target echo. The radar does see something (a broadened, noisy return), but cannot extract a usable range from it: the echo disappears somewhere inside the cover pulse.
- Difference from noise jamming: the jammer does not transmit continuously but only in a short window around its own echo — much more efficient with power (the duty-cycle logic of Peak power and average power of the pulse radar now works in the jammer's favour) and much less conspicuous than a continuous noise strobe.
- Difference from RGPO: no false range is offered; the information is erased, not falsified. The two are often combined: first a cover pulse to mask the real echo, then an RGPO walk to take the gate away in a controlled manner.
- Condition: timing. The jammer has to know when its own echo reaches the radar, so it must be able to predict the radar's pulse timing — once again PRI jitter (PRI modulation) is the natural counter, because with unpredictable pulses the cover comes too early or too late and the real echo sticks out next to it.
Cover pulses are also used to protect others: an escort jammer can lay its pulses over the echoes of the whole formation, and a stand-in jammer over the echoes of approaching weapons. The technique illustrates a general lesson: jamming does not have to shout — exactly enough energy, exactly on time, exactly on frequency is more effective and safer.