The 21-20-62 is a ruggedized VOR/Localiser/Glideslope antenna suitable for certain airborne and ground checking applications. For airborne use, the antenna can be mounted underneath an aircraft or helicopter fuselage where it can withstand ground and debris impact to a far greater extent than equivalent Vdipoles and other external antenna types. For ground use, the antenna provides a robust roof-mounted installation suitable for checking airfield VOR/ILS installations.

Electrical design uses a balanced loop giving excellent gain and circularity of azimuth pattern (forward sector only for Glideslope) whilst having greater rejection of unwanted vertical polarization. Constructed within a tough fiberglass radome, the antenna is fully sealed and foam filled for long term reliability.