GROL Filters and Frequency Control 2

Question 1

What component is primarily responsible for setting the resonant frequency in a crystal-controlled oscillator?

Accepted Answer

Quartz crystal

Answer

The quartz crystal's mechanical resonance determines the oscillator frequency with very high stability, overriding the effects of LC components.

Question 2

A Butterworth filter is characterized by which response?

Accepted Answer

Maximally flat passband with no ripple

Answer

A Butterworth filter provides a maximally flat (no ripple) frequency response in the passband, at the expense of a less steep initial rolloff compared to other designs.

Question 3

What is the cutoff frequency of a filter defined as?

Accepted Answer

The frequency at which output power is 3 dB below the passband level

Answer

The cutoff (or -3 dB) frequency is the point where output power falls to half (−3 dB) of the passband level, marking the boundary of the filter's pass region.

Question 4

In a parallel LC circuit at resonance, the impedance is:

Accepted Answer

Maximum (very high)

Answer

At resonance, a parallel LC (tank) circuit presents maximum impedance because the circulating current between L and C is self-sustaining, drawing minimal current from the source.

Question 5

What happens to the selectivity of a filter as its Q factor increases?

Accepted Answer

Selectivity increases

Answer

Higher Q means a narrower bandwidth relative to the center frequency, resulting in greater selectivity (ability to distinguish closely spaced signals).

(GROL) General Radiotelephone Operator License Practice Test

(GROL) General Radiotelephone Operator License Practice Test

GROL Filters and Frequency Control 2