A rectangular hollow metal waveguide of internal cross-section of $$7.366\,\,cm\,\, \times \,\,3.556\,cm$$ carries a 3 GHz signal in the $$T{E_{10}}$$-mode. Calculate the maximum power handling capability of the waveguide assuming the maximum permissible electric field inside the waveguide to be 30 kV/cm

Two spacecrafts are separated by 3000 km. Each has a paraboloidal reflector antenna of 0.85 m diameter operating at a frequency of 2 GHz with an aperture efficiency of 64%. If the space crafts A's receiver requires 1pW for a 20 dB signal-to-noise ratio, what transmitter power is required on the spacecraft B to achieve this signal-to-noise ratio?

For a dipole antenna