The 21-30-70 is a low profile UHF Satcom antenna that provides hemispherical coverage without the need to switch from high to low angle elements. The design comprises a pair of specially shaped crossed folded dipoles connected such as to generate Right Hand Circular polarization.

Typical radiation diagrams are shown overleaf. If enhanced near-horizon coverage is required, the antenna can be used in conjunction with a linearly polarized monopole antenna such as the CAL 21-30-18. Radome construction is from high strength epoxy-fiberglass and the antenna is sealed and foamed for long term protection against moisture ingress.