Key Topic 44: Mixers

Question 1

3-44F1: What is the image frequency if the normal channel is 151.000 MHz, the IF is operating at 11.000 MHz, and the LO is at 140.000 MHZ?

A. 131.000 MHz.
B. 129.000 MHz.
C. 162.000 MHz.
D. 150.000 MHz.

Answer 1

B. 129.000 MHz.

Question 2

3-44F2: What is the mixing process in a radio receiver?

A. The elimination of noise in a wideband receiver by phase comparison.
B. The elimination of noise in a wideband receiver by phase differentiation.
C. Distortion caused by auroral propagation.
D. The combination of two signals to produce sum and difference frequencies.

Answer 2

D. The combination of two signals to produce sum and difference frequencies.

Question 3

3-44F3: In what radio stage is the image frequency normally rejected?

A. RF.
B. IF.
C. LO.
D. Detector.

Answer 3

A. RF.

Question 4

3-44F4: What are the principal frequencies that appear at the output of a mixer circuit?

A. Two and four times the original frequency.
B. The sum, difference, and square root of the input frequencies.
C. The original frequencies, and the sum and difference frequencies.
D. 1.414 and 0.707 times the input frequency.

Answer 4

C. The original frequencies, and the sum and difference frequencies.

Question 5

3-44F5: If a receiver mixes a 13.8 MHz VFO with a 14.255 MHz receive signal to produce a 455 kHz intermediate frequency signal, what type of interference will a 13.345 MHz signal produce in the receiver?

A. Local oscillator interference.
B. An image response.
C. Mixer interference.
D. Intermediate frequency interference.

Answer 5

B. An image response.

Question 6

3-44F6: What might occur in a receiver if excessive amounts of signal energy overdrive the mixer circuit?

A. Automatic limiting occurs.
B. Mixer blanking occurs.
C. Spurious mixer products are generated.
D. The mixer circuit becomes unstable and drifts.

Answer 6

C. Spurious mixer products are generated.