How is the feed impedance of a dipole antenna determined?
The aim of any antenna is to radiate or “dissipate” as much power in this way as possible. As with any RF antenna, the feed impedance of a dipole antenna is dependent upon a variety of factors including the length, the feed position, the environment and the like.
How is loss resistance related to antenna feed impedance?
Antenna feed impedance resistive elements. The resistive elements are made up from two constituents. These add together to form the sum of the total resistive elements. Loss resistance: The loss resistance arises from the actual resistance of the elements in the aRF ntenna, and power dissipated in this manner is lost as heat.
How are coaxial feeders used to feed dipoles?
Feeding with 50Ω coaxial feeder is often a good compromise. For VHF / UHF dipoles, it is possible to raise them much higher, although mounting poles and masts may interact to reduce the impedance. Also dipoles are not often used on their own as they are often incorporated into antennas like the Yagi.
How is the impedance of a transmitter determined?
Most transmitters have a standard output impedance of 50 ohms, designed to feed 50 ohm coaxial cable The transmitter is matched to the feedline by a device called an antenna tuner, antenna tuning unit, or matching network, which may be a circuit in the transmitter, or a separate piece of equipment connected between the transmitter and feedline.
What causes RF to be picked up by a dipole?
This is typically achieved using an item called a balun: bal anced to un balanced.If a balun is not present, RF will be present on the outer of the coax and this can mean that the coax will radiate or pick up signals. This can lead to interference from appliances in the building being picked up, or interference caused by the transmitter.
Is it possible to feed a half wave dipole?
Although the most common for of dipole is the half wave dipole, others can be multiples of a half wavelength. It is therefore possible to feed the dipole at any one of these voltage minimum or current maximum points which occur at a point that is a quarter wavelength from the end, and then at half wavelength intervals.