The directivity of a small loop antenna is higher than that of a short dipole because the loop antenna is more directional and concentrates radiation in one direction. The ratio can vary depending on the dimensions and configuration of each antenna, but in general, the loop antenna can have a directivity several dB higher than the dipole.
Counterpoise is used in a dipole vertical antenna to improve its performance by providing a balanced electrical path for the antenna. This helps to reduce common-mode currents and improve the antenna's efficiency in transmitting and receiving signals. By using a counterpoise, the dipole antenna can achieve a better radiation pattern and impedance matching.
The radiation resistance of a folded dipole antenna is typically higher than that of a simple dipole antenna, approximately 300 ohms compared to 73 ohms. This increase in radiation resistance helps improve the efficiency and performance of the antenna. The folded design allows for a more compact structure while maintaining good radiation characteristics.
The length of a dipole antenna directly affects its resonant frequency; a longer antenna typically resonates at a lower frequency, while a shorter antenna resonates at a higher frequency. This is because the length of the antenna is generally optimized to be around half the wavelength of the frequency it is intended to transmit or receive. Additionally, changes in length can impact the antenna's impedance, bandwidth, and radiation pattern. Therefore, adjusting the length alters its efficiency and performance for specific frequency ranges.
It experiences a torque but no force. As the dipole is placed at an angle to the direction of a uniform electric field it experiences two opposite and equal forces which are not along the same line. This develops a torque which aligns the dipole along the field. The dipole does not experience any force as the two forces cancel each other.
The directivity of a small loop antenna is higher than that of a short dipole because the loop antenna is more directional and concentrates radiation in one direction. The ratio can vary depending on the dimensions and configuration of each antenna, but in general, the loop antenna can have a directivity several dB higher than the dipole.
A folded antenna is a dipole type.
effective height of half wave dipole antenna
Depends on what you mean by high frequency. The rabbit ears antenna used in broadcast TV is a dipole and is used for VHF.
I don't think it has. Bandwidth depends on the diameter to length ratio of the antenna. The greater the diameter of the elements the wider the bandwidth. The inductance goes down and the capacitance goes up, giving the antenna a lower Q. the folded dipole has a greater effective diameter (at least double for the same materials). You can increase a normal dipole's bandwidth by increasing the diameter, hence the old time birdcage aerials.
Dipole
A full-wave loop antenna can be interchanged with a folded dipole without much difference. The input impedance is similar and the only difference is in the directivity: a full wave loop radiates along the axis of the loop, while a vertical folded dipole is omnidirectional.
245
The direction of the dipole moment of an electric dipole from negative to positive charge is chosen as a convention to align with the direction of the electric field produced by the dipole. This convention allows for easy calculation and understanding of how the dipole interacts with external electric fields.
Loop antenna generate the same field as electrical dipole, but E and H are exchanged (a proof can be obtained this way: you align an electrical dipole with an axis, say z, and a loop antenna with z - you have to define surface orientation - then you apply duality theorem, calculate far field and you got it). For instance, in spherical coordinates (r,phi,theta) you have el. dipole {Etheta,Hphi} loop ant. {Ephi,Htheta} So, you can superpose the two fields and see that you have gained polarization independency (if an electrical dipole is aligned with z-axis and has its gap at z=0, it will receive very well Etheta, not at all Ephi (plane z=0), if you put a loop antenna "around" electrical dipole - like a ring around dipole's gap, lying on z=0 plane - it will receive very well Ephi (plane z=0) ). This is the way to make triaxial sensor, which have to be polarization independent.
Counterpoise is used in a dipole vertical antenna to improve its performance by providing a balanced electrical path for the antenna. This helps to reduce common-mode currents and improve the antenna's efficiency in transmitting and receiving signals. By using a counterpoise, the dipole antenna can achieve a better radiation pattern and impedance matching.
36 ohm