The 21-50-43 is a dual band VHF/UHF communications antenna intended for use on high speed aircraft . Its construction is from precision machined aluminium alloy with high strength glass/epoxy inserts. Having a low profile diamond shape raked blade structure minimizes drag for high speed applications and presents a low Radar Cross Section (RCS). The aluminium structure also lends itself to the application of certain types of ’stealth’ radar absorbing material.

The electrical design comprises a UHF sleeved unipole, the upper element of which acts as a "choke" enabling a capacitive horizontal rod to operate as a top loaded VHF monopole, decoupled from the UHF section.

Designed and constructed to meet MIL-STD-810 environmental conditions, the 21-50-43 is a drop-on footprint replacement for UHF blade type AT-256, having a single N-type Female connector. The antenna is normally finished in lusterless grey urethane paint.