Skip zone

In telecommunication, a skip zone is an annular region within the transmission range of an antenna, within which signals from the transmitter are not received.

Note: The skip zone is bounded by the locus of the farthest points at which the ground wave can be received and the nearest points at which reflected sky waves can be received. Synonyms silent zone, zone of silence.

Source: from Federal Standard 1037C and from MIL-STD-188