Q3·TV signals are broadcast using UHF radio waves, with wavelengths of 1 cm to 1
ID: 2265645 • Letter: Q
Question
Q3·TV signals are broadcast using UHF radio waves, with wavelengths of 1 cm to 1 m. The two images below show a typical TV broadcast antenna, and typical rooftop reception antennas A UHF broadcast mast Household UHF antennas (ignore the satellite dishes!) With reference to the principle of reciprocity, please explain: Why the broadcast antenna is a dipole type design, while the receivers are Yagi-Uda types. Would it work well if the transmit and receive antennas were swapped? (a) (b) Why the receiver antennas are all pointing in a similar direction?Explanation / Answer
The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole with a radiating structure supporting a line current so energized that the current has only one node at each end.The receivers are Yagi uda becauseThe Yagi-Uda antenna or Yagi Antenna is one of the most brilliant antenna designs. It is simple to construct and has a highgain, typically greater than 10 dB.
The Yagi antenna design has a dipole as the main radiating or driven element. Further 'parasitic' elements are added which are not directly connected to the driven element.
These parasitic elements within the Yagi antenna pick up power from the dipole and re-radiate it.
The phase is in such a manner that it affects the properties of the RF antenna as a whole, causing power to be focussed in one particular direction and removed from others.power in specific directions allowing for increased performance and reduced interference from unwanted sources.
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