Ques.1. Which of the following is NOT true with respect to antennas?
Ques.2. A Cassegrain reflector antenna has a sub-reflector whose geometrical shape is:
Ques.3. To make antenna more directional, either its size must be increased or
- The number of its feed horns must be increased
- The frequency of its transmission must be increased
- Its effective isotropic radiated power (eirp) must be increased
- Its footprint must be increased
Ques.4. Two isotropic antennas are separated by a distance of two wavelengths. If both the antennas are fed with currents of equal phase and magnitude, the number of lobes in the radiation pattern in the horizontal plane are
Ques.5. An antenna has 40 Ω antenna resistance and 60 Ω radiation resistance. The efficiency of the antenna will be
Ques.6. The half-power beam width (HPBW) of an antenna in the two orthogonal planes are 120º and 40º respectively. The directivity of the antenna is approximately equals to
- 10 dB
- 6.5 dB
- 12 dB
- 8.5 dB
Ques.7. What is the length of the antenna needed for a signal of 500 KHz frequency?
- 6 km
- 150 m
- 600 m
- 1 km
Ques.8. A short current element has a length l = 0.03 λ, where λ is the wavelength. The radiation resistance for uniform current distribution is
- 0.072π2 Ω
- 80π2 Ω
- 72 Ω
- 80 Ω
Ques.9. What should be the length of the transmitting Antenna for radiating radio waves of 900 MHz?
- 16.7 cm
- 1.67 cm
- 8.3 cm
- None of the above
Ques.10. Assertion (A): A Cassegrain antenna uses a main paraboloidal reflector and a relatively small hyperboloidal sub-reflector with a small horn-feed at the vertex of the main paraboloidal reflector.
Reason (R): The optical technique developed by William Cassegrain was used in telescope design to obtain large magnification with a physically short telescope. This configuration is found to be effective in the design of microwave antennas also.