Amateur ExtraE9A01
What is an isotropic radiator?
C
Answer
Antennas and transmission lines
Type
A
A calibrated, unidirectional antenna used to make precise antenna gain measurements
B
An omnidirectional, horizontally polarized, precisely calibrated antenna used to make field measurements of antenna gain
C
A hypothetical, lossless antenna having equal radiation intensity in all directions used as a reference for antenna gain
D
A spacecraft antenna used to direct signals toward Earth
Answer Notes
An isotropic radiator is a purely theoretical, mathematical concept used in antenna engineering. It is defined as a hypothetical point source in space that radiates electromagnetic energy equally in all directions, creating a perfect sphere of radiation.
Because no such antenna can physically exist, its primary purpose is to serve as a universal baseline or reference point (0 dBi) for measuring and comparing the directional gain of real-world antennas.
The distractors all describe physical antennas or instruments used in the real world. Remember that any mention of an 'isotropic' antenna must be associated with a hypothetical or theoretical model.
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What is the effective radiated power (ERP) of a repeater station with 150 watts transmitter power output, 2 dB feed line loss, 2.2 dB duplexer loss, and 7 dBd antenna gain?