-
Know that the gain of an antenna is measured in dB,
and understand how to calculate the e.r.p. for a known RF power and antenna
gain (in multiples of 3 dB).
-
Know that a three-element yagi has a half-wave
driven element, a reflector that is slightly longer than the driven element
and a director that is slightly shorter than the driven element.
-
Know that yagi antennas may have more than one
director.
-
Know that electromagnetic radiation comprises
both an electrical field and a magnetic field.
-
Know that the two fields are at right-angles to each
other and that the direction of propagation is at right-angles to both fields.
-
Know that it is the electrical field that defines
polarisation of the wave.
-
Know that VHF and UHF signals will normally be
received best when the transmitter and the receiver have the same antenna
polarisation.
-
Know that polarisation is less important at HF due
the effects of ionospheric reflection.
-
Know the concept of an antenna polar diagram.
-
Know how to recognise the directions of maximum and
minimum radiation.
-
Know how to recognise polar diagrams for the
half-wave dipole and yagi antennas.
-
Know the use of a dummy load and its construction.