For a 3-element Yagi antenna with horizontally mounted elements, how does the main lobe takeoff angle vary with height above flat ground?

Most simple horizontally polarized antennas do not exhibit any directivity unless they are:

The plane from which ground reflections can be considered to take place, or the effective ground plane for an antenna is:

Why is a ground-mounted vertical quarter-wave antenna in reasonably open surroundings better for long distance contacts than a half-wave dipole at a quarter wavelength above ground?

When a half-wave dipole antenna is installed one-half wavelength above ground, the:

How does antenna height affect the horizontal (azimuthal) radiation pattern of a horizontal dipole HF antenna?

For long distance propagation, the vertical radiation angle of the energy from the antenna should be:

Greater distance can be covered with multiple-hop transmissions by decreasing the:

The impedance at the centre of a dipole antenna more than 3 wavelengths above ground would be nearest to:

What is the main reason why so many VHF base and mobile antennas are 5/8 of a wavelength?

The most important consideration when deciding upon an antenna for contacting stations at great distances (DX) is: