Half-dipole (antenna)

A rectilinear dipole antenna whose total electrical length is about half wavelength.

Harmful interference

Interference which endangers the functioning of a radionavigation service or of other safety services or seriously degrades, obstructs, or repeatedly interrupts a radiocommunication service operating in accordance with Radio Regulations.

HCM Agreement

Agreement, under Article 6 of the Radio Regulations, on the co-ordination of frequencies between 29.7 MHz and 43.5 GHz for the purposes of preventing mutual harmful interference to the Fixed and Land Mobile Services and optimising the use of the frequency spectrum. This Agreement has been concluded by the representatives of the 17 European countries.

Horizontal polarisation

Type of linear polarisation, at which electric vector vibrations take place horizontally to the reference plane (usually Earth’s surface).