8-38D: Miscellaneous

Question 1

8-38D3

In order to ensure that a practical filter is able to remove undesired components from the output of an analog-to-digital converter, the sampling frequency should be:

A. The same as the lowest component of the analog frequency.
B. Two times the highest component of the analog frequency.
C. Greater than two times the highest component of the sampled frequency.
D. The same as the highest component of the sampled frequency.

Answer 1

ANSWER C
According to the Nyquist Theorem, to correctly represent the analog signal, the sampling frequency must be great than two times the highest frequency of the analog signal being sampled.

Question 2

8-38D6

How do you eliminate stationary objects such as trees, buildings, bridges, etc., from the PPI presentation?

A. Remove the discriminator from the unit.
B. Use a discriminator as a second detector.
C. Calibrate the IF circuit.
D. Calibrate the local oscillator.

Answer 2

ANSWER B
For RADAR installations used on land for the vessel traffic system (VTS), using a discriminator as a second detector is one way to minimize return echoes from stationary objects.