FCC2 COPY

Question 1

What is the definition of the term “receiver desensitizing”?

Answer 1

A reduction in receiver sensitivity because of a strong signal on a nearby frequency.

Question 2

What is the advantage of a GaAsFET preamplifier in a modern VHF radio receiver?

Answer 2

High gain and low noise floor.

Question 3

What condition must exist for a circuit to oscillate? It must:

Answer 3

Have sufficient positive feedback.

Question 4

In what radio stage is the image frequency normally rejected?

Answer 4

RF.

Question 5

How should the filter bandwidth of a receiver IF section compare with the bandwidth of a received signal?

Answer 5

Slightly greater than the received-signal bandwidth.

Question 6

What is the limiting condition for sensitivity in a communications receiver?

Answer 6

The noise floor of the receiver.

Question 7

Too much gain in a VHF receiver front end could result in this:

Answer 7

Susceptibility of intermodulation interference from nearby transmitters.

Question 8

What are the principal frequencies that appear at the output of a mixer circuit?

Answer 8

The original frequencies and the sum and difference frequencies.

Question 9

A receiver selectivity of 10 kHz in the IF circuitry is optimum for what type of signals?

Answer 9

Double-sideband AM.

Question 10

Which stage of a receiver primarily establishes its noise figure?

Answer 10

The RF stage.

Question 11

Which type of oscillator circuit is commonly used in a VFO (variable frequency oscillator)?

Answer 11

Colpitts.

Question 12

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?

Answer 12

129,000 MHz.

Question 13

A receiver selectivity of 10 KHz i the IF circuitry is optimum for what type of signals?

Answer 13

Double-sideband AM.

Question 14

What is the term used to refer to a reduction in receiver sensitivity caused by unwanted high-level adjacent channel signals?

Answer 14

Desensitizing.

Question 15

In what stage of a VHF receiver would a low noise amplifier be most advantageous?

Answer 15

Front end RF stage.

Question 16

What are the three major oscillator circuits found in radio equipment?

Answer 16

Colpitts, Hartley, and Pierce.

Question 17

If a receiver mixed 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?

Answer 17

An image response.

Question 18

Which one of these filters can be used in micro-miniature electronic circuits?

Answer 18

Receiver SAW IF filter.

Question 19

What is the definition of the term “receiver desensitizing”?

Answer 19

A reduction in receiver sensitivity because of a strong signal on a nearby frequency.

Question 20

What is the mixing process in a radio receiver?

Answer 20

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

Question 21

What is an undesirable effect of using too wide a filter bandwidth in the IF section of a receiver?

Answer 21

Undesired signals will reach the audio stage.

Question 22

In Figure 3F15, which block diagram symbol (labeled 1 through 4) is used to represent a local oscillator?

Answer 22

2

Question 23

How can selectivity be achieved in the front-end circuitry of a communications receiver?

Answer 23

By using a preselector.

Question 24

Why is the Colpitts oscillator circuit commonly used in a VFO (variable frequency oscillator)?

Answer 24

It is stable.

Question 25

In what radio stage is the image frequency normally rejected?

Answer 25

RF.

Question 26

How should the filter bandwith of a receiver IF section comppare with the bandwidth of a received signal?

Answer 26

Slightly greater than the received-signal bandwidth.

Question 27

What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal?

Answer 27

Dynamic range.

Question 28

Too much gain in a VHF receiver front end could result in this:

Answer 28

Susceptibility of intermodulation interference from nearby transmitters.

Question 29

If a receiver mixed 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?

Answer 29

An image response.

Question 30

What is the primary purpose of an RF amplifier in a receiver?

Answer 30

To improve the receiver’s noise figure.

Question 31

What are the principal frequencies that appear at the output of a mixer circuit?

Answer 31

The original frequencies and the sum and difference frequencies.

Question 32

What degree of selectivity is desirable inn the IF circuitry of a wideband FM phone receiver?

Answer 32

15 kHz.

Question 33

What is the oscillator stage called i a frequency synthesizer?

Answer 33

VCO.

Question 34

What is the primary purpose of an RF amplifier in a receiver?

Answer 34

To improve the receiver’s noise figure.

Question 35

What is meant by the term noise figure of a communications receiver?

Answer 35

The level of noise generated in the front end and succeeding stages of a receiver.

Question 36

How much gain should be used in the RF amplifier stage of a receiver?

Answer 36

Sufficient gain to allow weak signals to overcome noise generated in the first mixer stage.

Question 37

Which type of oscillator circuit is commonly used in a VFO (variable frequency oscilator)?

Answer 37

Colpitts.

Question 38

What is an undesirable effect of using too wide a fiter bandwidth in the IF section of a receiver?

Answer 38

Undesired signals will reach the audio stage.

Question 39

What might occur in a receiver if excessive amounts of signal energy overdrive the mixer circuit?

Answer 39

Spurious mixer products are generated.