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28 kwi 2023 · Given the high quality of today’s transceivers, the most important station component is the antenna system that starts at the RF connector of your radio and ends a wavelength or two away. Gains and losses anywhere in the system affect signal strength.
THE HAND-HELD RADIO ANTENNA DILEMMA – 3 – •Extending just the antenna on a coax jumper, as is common in various ‘suitcase’ go-kits may make the stray RF problem even worse by increasing the stray RF surface area by coax shield. •The radiation pattern in such cases is ambiguous and not optimal. (C)2016 - NO1PC, JIM ASPINWALL
The radiation pattern shows how antennas distribute energy in space. deciBels (dB) = 10 log (power ratio) Impedance = ratio of Voltage to Current. Feed point - place where power is applied. -1 dB from the maximum gain reference value. Azimuthal Pattern. Elevation Pattern. Front-to-Back, Front-to-Side, and Front-to-Rear ratios.
OW ELEVATION ANGLE(a in Fig, 6). Therefore, to judge antenna performance, it is more useful to have an antenna pattern showing the radiation at 30. egrees or more above the horizon. Figure 8 is a diagram showing the signal strength (represented by vectors) radiated from a typical half-wave dipole anten.
NOTE 1 – Part 1 to Annex 1 gives comprehensive and detailed information on the theoretical characteristics of HF transmitting antennas. Computer programs have been developed from the theory to calculate the radiation patterns and gain for the various included antenna types.
The radiation pattern for an antenna is defined on this page. We have 3D graphs of real antenna radiation patterns, with a discussion on isotropic, omnidirectional and directional radiation patterns.
In HF broadcasting the antenna is the means by which the radio-frequency energy is directed towards the required service area. The selection of the right type of antenna will enhance the signal in this area, while reducing radiation in unwanted directions.
