FCC2 Flashcards
Study for FCC exam
What is the definition of the term “receiver desensitizing”?
A reduction in receiver sensitivity because of a strong signal on a nearby frequency.
What is the advantage of a GaAsFET preamplifier in a modern VHF radio receiver?
High gain and low noise floor.
What condition must exist for a circuit to oscillate? It must:
Have sufficient positive feedback.
In what radio stage is the image frequency normally rejected?
RF.
How should the filter bandwidth of a receiver IF section compare with the bandwidth of a received signal?
Slightly greater than the received-signal bandwidth.
What is the limiting condition for sensitivity in a communications receiver?
The noise floor of the receiver.
Too much gain in a VHF receiver front end could result in this:
Susceptibility of intermodulation interference from nearby transmitters.
What are the principal frequencies that appear at the output of a mixer circuit?
The original frequencies and the sum and difference frequencies.
A receiver selectivity of 10 kHz in the IF circuitry is optimum for what type of signals?
Double-sideband AM.
Which stage of a receiver primarily establishes its noise figure?
The RF stage.
Which type of oscillator circuit is commonly used in a VFO (variable frequency oscillator)?
Colpitts.
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?
129,000 MHz.
A receiver selectivity of 10 KHz i the IF circuitry is optimum for what type of signals?
Double-sideband AM.
What is the term used to refer to a reduction in receiver sensitivity caused by unwanted high-level adjacent channel signals?
Desensitizing.
In what stage of a VHF receiver would a low noise amplifier be most advantageous?
Front end RF stage.
What are the three major oscillator circuits found in radio equipment?
Colpitts, Hartley, and Pierce.
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?
An image response.
Which one of these filters can be used in micro-miniature electronic circuits?
Receiver SAW IF filter.
What is the definition of the term “receiver desensitizing”?
A reduction in receiver sensitivity because of a strong signal on a nearby frequency.
What is the mixing process in a radio receiver?
The combination of two signals to produce sum and difference frequencies.
What is an undesirable effect of using too wide a filter bandwidth in the IF section of a receiver?
Undesired signals will reach the audio stage.
In Figure 3F15, which block diagram symbol (labeled 1 through 4) is used to represent a local oscillator?
2
How can selectivity be achieved in the front-end circuitry of a communications receiver?
By using a preselector.
Why is the Colpitts oscillator circuit commonly used in a VFO (variable frequency oscillator)?
It is stable.
In what radio stage is the image frequency normally rejected?
RF.
How should the filter bandwith of a receiver IF section comppare with the bandwidth of a received signal?
Slightly greater than the received-signal bandwidth.
What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal?
Dynamic range.
Too much gain in a VHF receiver front end could result in this:
Susceptibility of intermodulation interference from nearby transmitters.
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?
An image response.
What is the primary purpose of an RF amplifier in a receiver?
To improve the receiver’s noise figure.
What are the principal frequencies that appear at the output of a mixer circuit?
The original frequencies and the sum and difference frequencies.
What degree of selectivity is desirable inn the IF circuitry of a wideband FM phone receiver?
15 kHz.
What is the oscillator stage called i a frequency synthesizer?
VCO.
What is the primary purpose of an RF amplifier in a receiver?
To improve the receiver’s noise figure.
What is meant by the term noise figure of a communications receiver?
The level of noise generated in the front end and succeeding stages of a receiver.
How much gain should be used in the RF amplifier stage of a receiver?
Sufficient gain to allow weak signals to overcome noise generated in the first mixer stage.
Which type of oscillator circuit is commonly used in a VFO (variable frequency oscilator)?
Colpitts.
What is an undesirable effect of using too wide a fiter bandwidth in the IF section of a receiver?
Undesired signals will reach the audio stage.
What might occur in a receiver if excessive amounts of signal energy overdrive the mixer circuit?
Spurious mixer products are generated.
