Free Electronics and Devices MCQs with Answers

• A. The difference frequency is closer to oscillator frequency
• B. Lower frequencies are easier to amplify
• C. Only the difference frequency can be modulated
• D. None of the above

Explanation: The difference frequency is selected as the intermediate frequency because it is lower and can be amplified and filtered conveniently with…

• A. Radio frequency
• B. IF
• C. Audio frequency
• D. None of the above

Explanation: A TRF receiver amplifies the incoming signal directly at its radio frequency, with the tuned circuits tracking that frequency.

• A. Amplitude
• B. Frequency
• C. Phase
• D. None of the above

Explanation: Television sound is normally transmitted using frequency modulation, which provides better noise immunity than AM.

• A. Before the first RF stage
• B. After the first RF stage
• C. After several stages of amplification
• D. None of the above

Explanation: The diode detector is placed after RF and usually IF amplification so that it receives a sufficiently strong modulated signal.

• A. Amplitude of the carrier
• B. Frequency of the carrier
• C. Phase of the carrier
• D. May be any of the above

Explanation: Modulation means varying a carrier parameter according to the information signal.

• A. Reception is less noisy
• B. Higher carrier frequency
• C. Smaller bandwidth
• D. Small frequency deviation

Explanation: FM has strong resistance to amplitude noise because the information is carried by frequency changes, and limiting circuits can remove…

• A. Using a large number of amplifier stages
• B. Using a push-pull circuit
• C. Obtaining lower fixed intermediate frequency
• D. None of the above

Explanation: A superheterodyne receiver mixes the incoming signal with a local oscillator to produce a lower, fixed intermediate frequency.

• A. RF
• B. IF
• C. audio
• D. Before RF

Explanation: Mixing translates the selected station to a fixed intermediate frequency, where sharply tuned IF filters provide most of the receiver's…

• A. IF
• B. RF amplifier
• C. Audio amplifier
• D. Detector

Explanation: The IF amplifier is designed for high, stable gain at one fixed frequency, so several cascaded IF stages provide most of the receiver…

• A. Sensitivity
• B. Selectivity
• C. Distortion
• D. Fidelity

Explanation: Fidelity describes how accurately a receiver reproduces the entire range of signal frequencies, so equal amplification indicates high…

• A. Audio voltage control
• B. Abrupt voltage control
• C. Automatic volume control
• D. Automatic voltage control

Explanation: AVC means automatic volume control, a receiver circuit that adjusts gain as received signal strength changes.

• A. IF and RF
• B. RF and AF
• C. IF and AF
• D. RF and local oscillator signal

Explanation: The mixer combines the incoming RF signal with the local oscillator signal, producing sum and difference frequencies.

• A. Phase modulation
• B. Amplitude modulation
• C. Frequency modulation
• D. May be any one of the above

Explanation: Frequency modulation occurs when the instantaneous frequency of the carrier varies according to the modulating signal.

• A. 455 kHz
• B. 1310 kHz
• C. 1500 kHz
• D. 1520 kHz

Explanation: For the usual high-side injection, the local oscillator is set to signal frequency plus IF: 855 + 455 = 1310 kHz.

• A. Reduce stray capacitance
• B. Stabilise d.c. bias
• C. Increase the Q of tuned circuit
• D. Reduce noise

Explanation: A ferrite rod increases the inductance and magnetic flux linkage of the coil, allowing a compact tuned antenna with a higher Q and better…

• A. 20 %
• B. 40 %
• C. 50 %
• D. 10 %

Explanation: Using m = (Amax − Amin)/(Amax + Amin), m = (60 − 40)/(60 + 40) = 0.20. Therefore the percentage modulation is 20%, not 40% or 50%.

• A. Crystal
• B. Wien-bridge
• C. Phase-shift
• D. Hartley

Explanation: A Hartley oscillator is commonly used as a receiver local oscillator because its tuned LC circuit provides convenient frequency adjustment…

• A. 50 kW
• B. 5 kW
• C. 8 kW
• D. 25 kW

Explanation: In amplitude modulation, the carrier power remains constant at all modulation depths; only the sideband power changes.

• A. Is increased
• B. Remains the same
• C. Is decreased
• D. None of the above

Explanation: The carrier amplitude and power are set by the unmodulated carrier and do not change with modulation depth.

• A. Fidelity
• B. Frequency range
• C. Sensitivity
• D. Selectivity

Explanation: A high-Q tuned circuit has a narrow bandwidth and strongly rejects frequencies away from resonance.