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H

HAAT : Height Above Average Terrain.

Harmonic : Integer multiples of the fundamental frequency being generated, harmonics are present if a signal is not perfectly sinusoidal or is undergoing intermodulation distortion. Harmonics located outside the desired band for transmission are normally removed with low-pass filters to avoid interference to other radio services.

Half Duplex : The ability for a transceiver to transmit and receive on two different frequencies, but ony one of these at any given time.

Half wave dipole : An antenna that is half a wavelength total, fed at the centre.

HASL : Height Above Sea Level. Often used for mountaintop stations such as repeaters and portable operations to describe their elevation. Measured in either feet or metres depending on the country.

hamfest : An event at which hams can buy sell and swap equipment. Often held in conjuction with lectures and demonstrations of equipment.

Harmonic : An integer multiple of a frequency

Harmonic (of a ham)  : Slang term for the child of a ham.

Hellschreiber (Hell) : A digital mode for sending and receiving text using facsimile (fax) technology.

Henry :(H) The unit for inductance

Hertz : Hz - The unit of measure for frequency. Named after Heinrich Hertz

HF : High Frequency. Frequencies in the range 3MHz to 30MHz, also known as shortwave.

High Pass Filter : A filter designed to pass high frequency signals.

hi hi : The morse equivalent of laughter.

Homebrew : Home built equipment.

Horizontal Polarization : An antenna which projects a radio signal in which the electric field is parallel to the surface of the earth OR a radio signal of which the electric field is propagated parallel to the surface of the Earth.

HT (1) : Handheld Transceiver or HandiTalkie. Usually refers to transceivers that operate in the 2m and 70cm amateur bands; these are self-contained hand-held radios which include an antenna and battery and transmit at low power.

HT (2) : High Tension Voltage. Voltages over 500V