Noun
a signal transmitted along a narrow path; guides airplane pilots in darkness or bad weather
Source: WordNetAnd for harder targets, up to four 9M120 Ataka-V or 9M114 Shturm-V radio beam anti-tank guided missiles (ATGM) were usually carried. Source: Internet
The Doctor has that the Cybermen fleet need a radio beam to focus on to navigate to Earth. Source: Internet