In a uniform linear array, four isotropic radiating elements are spaced $$\lambda /4$$ apart. The progressive phase shift between the elements required for forming the main beam at 60° off the end-fire is

A medium wave radio transmitter operating at a wavelength of 492 m has a tower antenna of height 124m. What is the radiation resistance of the antenna?

A rectangular hollow metal waveguide has dimensions a = 2.29 cm and b = 1.02 cm. Microwave power at 10 GHz is transmitted through the waveguide in the $$T{E_{10}}$$ mode.
(a) Calculate the cut-off wavelength and the guide wavelength for this mode.
(b) What are the other (TE or TM) modes that can propagate through the waveguide?
(c) If a = b = 2.29 cm, what are the modes which can propagate through the waveguide?

A material has conductivity of 10^-2 mho/m and a relative permittivity of 4. The frequency at which the conduction current in the medium is equal to the displacement current is