In a half-wave dipole antenna, the highest distribution of current occurs at the middle of the antenna. This is where the current is maximized, and it gradually decreases towards the ends.

The physical length of a coaxial cable is shorter than its electrical length because RF energy travels more slowly along the coaxial cable than in free space (air). This reduction in velocity results in a shorter physical length for a given electrical length.

Antenna percent efficiency is calculated as the ratio of the radiation resistance to the total resistance of the antenna system, multiplied by 100. It represents the efficiency of the antenna in converting input power into radiated power.

As the standing wave ratio (SWR) increases, more energy is reflected back from the mismatched load (antenna), and this energy can cause additional losses in the transmission line. These losses are primarily due to dielectric and conductor heating caused by the higher voltage and current associated with reflected power.

A typical velocity factor for coaxial cable with polyethylene dielectric is approximately 0.66. The velocity factor varies depending on the type of dielectric material used in the cable.

The radiation resistance of an antenna is determined by factors such as the antenna’s location with respect to nearby objects and the length-to-diameter ratio of the antenna elements. These factors affect how efficiently the antenna radiates electromagnetic energy.

A 3 dB gain antenna represents a doubling of power (2 times), while a 9 dBd gain antenna represents approximately an 8-fold increase in power (8 times). Therefore, when replacing a 3 dB gain antenna with a 9 dBd gain antenna, the ERP will increase by a factor of (8 / 2) = 4 times.

Effective Radiated Power (ERP) is calculated by subtracting the losses (transmission line loss) from the transmitter output power and adding the antenna gain.

A quarter-wavelength transmission line presents a very low impedance when it is open at the far end. This is because at a quarter-wavelength, the voltage at the far end is at its minimum, and the current is at its maximum, resulting in a low impedance point.

Waveguide is an efficient transmission medium because it features low radiation loss, low dielectric loss, and low copper loss. Hysteresis loss is not typically associated with waveguide.

In a Yagi antenna with a gamma match, the coaxial cable’s braid connects to the center of the driven element, and the center conductor is connected to a variable capacitor and an adjustable mechanical arrangement on one side of the driven element. This arrangement helps match the antenna to the transmission line.

Circularly polarized electromagnetic waves are characterized by a rotating electric field. Unlike linear polarization, where the electric field oscillates in a single plane, circular polarization involves a rotating electric field vector as the wave propagates

A helical-beam antenna is capable of responding simultaneously to both vertically- and horizontally-polarized signals. This dual-polarization capability makes helical antennas versatile for various signal receptions.

The effective ground plane for an antenna is typically considered to be several centimeters to as much as 2 meters below the ground surface, depending on soil conditions. This effective ground plane is where ground reflections can be considered to take place and affects the antenna’s performance.

An antenna tuner of the “Series” type is not referred to as a Pi-type antenna tuner. Instead, it is typically known as a Series-type antenna tuner. This type of tuner is suitable for matching a wide range of antenna impedances to the 50-ohm transmitter input.

At the ends of a half-wave dipole antenna, the voltage is high, and the current is low. This voltage distribution results in the characteristic behavior of a half-wave dipole.

Effective Radiated Power (ERP) is calculated by subtracting the losses (transmission line loss and transmatch loss) from the transmitter output power and adding the antenna gain.

A network transforms one impedance to another by canceling the reactive part of the impedance while changing the resistive part. This impedance transformation allows efficient power transfer and impedance matching in various RF applications.

The total resistance of an antenna system includes both the radiation resistance (which contributes to the radiated power) and the ohmic resistance (which represents losses in the antenna elements and feed line). Together, these resistances make up the total resistance of the system.

In amateur work, it is advisable not to exceed a surface error upper limit of 0.1 wavelength (0.1 lambda) on a parabolic reflector. Surface error refers to imperfections in the shape of the reflector, and keeping it within this limit ensures good performance.

When linearly-polarized antennas are crossed-polarized (90 degrees) with each other, significant signal loss of 20 dB or more can be expected in theory. This is due to the mismatch in polarization, where the antennas are oriented perpendicularly to each other.

Crossed dipoles fed 90 degrees out of phase produce circular polarization. Circular polarization involves the electric field changing direction in a rotary manner as the wave propagates.

Among the options listed, a pi-network offers the greatest transformation ratio for impedance matching. Pi-networks are versatile and commonly used for matching a wide range of antenna impedances to the desired source or load impedance.

The impedance of a half-wave antenna at its center is low because, at this point, the voltage is low, and the current is high. This combination of low voltage and high current results in a lower impedance.

In a half-wave dipole antenna, the minimum voltage occurs at the center of the antenna. This is the point where the voltage is minimized compared to other parts of the antenna.