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Subelement F
Receivers
Section 41
Receiver Theory
What is the limiting condition for sensitivity in a communications receiver?
  • Correct Answer
    The noise floor of the receiver.
  • The power supply output ripple.
  • The two-tone intermodulation distortion.
  • The input impedance to the detector.

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

The noise floor of the receiver.

The receiver picks up the signal and noise. Without the radio signal, all you hear is the noise background. The radio frequency has to be above the noise power.

RF cannot be received below the noise level, referred to as the noise floor. At the noise floor, the noise level is measured in dBm/Hz, usually within a 1 Hz bandwidth.

For more information, please see the Electronics Notes site for the article What is Noise Floor for radio receivers and also the article Radio Signal to Noise S/N Ratio, SNR

Also, see the High Frequency Electronics site for the article Receiver Sensitivity and Equivalent Noise Bandwidth

For details on the noise, please see the RSGB org site for the pdf article on The Background Noise on the HF Amateur Bands

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What is the definition of the term “receiver desensitizing”?
  • A burst of noise when the squelch is set too low.
  • Correct Answer
    A reduction in receiver sensitivity because of a strong signal on a nearby frequency.
  • A burst of noise when the squelch is set too high.
  • A reduction in receiver sensitivity when the AF gain control is turned down.

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

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

The squelch button is used to control the level of noise coming in with the radio signal. But, too much will also suppress the radio signal itself, as in too much of a good thing.

See Wikipedia's article on Desensitization (telecommunications)

Also, see the Electronic Notes site for the article on Radio Blocking & Desensitisation

And, see the RF Wireless World site for the article on What is receiver blocking?

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What is the term used to refer to a reduction in receiver sensitivity caused by unwanted high-level adjacent channel signals?
  • Correct Answer
    Desensitizing.
  • Intermodulation distortion.
  • Quieting.
  • Overloading.

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

Desensitizing.

The squelch button is used to control the level of noise coming in with the radio signal. But, too much will also suppress the radio signal itself, as in too much of a good thing.

See Wikipedia's article on Desensitization (telecommunications)

Also, see the Electronic Notes site for the article on Radio Blocking & Desensitisation

And, see the RF Wireless World site for the article on What is receiver blocking?

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What is meant by the term noise figure of a communications receiver?
  • The level of noise entering the receiver from the antenna.
  • The relative strength of a received signal 3 kHz removed from the carrier frequency.
  • Correct Answer
    The level of noise generated in the front end and succeeding stages of a receiver.
  • The ability of a receiver to reject unwanted signals at frequencies close to the desired one.

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.

The squelch button is used to control the level of noise coming in with the radio signal. But, too much will also suppress the radio signal itself, as in too much of a good thing.

See Wikipedia's article on Desensitization (telecommunications)

Also, see the Electronic Notes site for the article on Radio Blocking & Desensitisation

And, see the RF Wireless World site for the article on What is receiver blocking?

For more information, please see the Electronics Notes site for the article What is Noise Floor for radio receivers and also the article Radio Signal to Noise S/N Ratio, SNR

Also, see the High Frequency Electronics site for the article Receiver Sensitivity and Equivalent Noise Bandwidth

For details on the noise, please see the RSGB org site for the pdf article on The Background Noise on the HF Amateur Bands

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Which stage of a receiver primarily establishes its noise figure?
  • The audio stage.
  • Correct Answer
    The RF stage.
  • The IF strip.
  • The local oscillator.

Which stage of a receiver primarily establishes its noise figure?

The RF stage.

For more information, please see the Electronics Notes site for the article What is Noise Floor for radio receivers and also the article Radio Signal to Noise S/N Ratio, SNR and the article What is Noise Figure - measurement & formula

Also, see the High Frequency Electronics site for the article Receiver Sensitivity and Equivalent Noise Bandwidth

For details on the noise, please see the RSGB org site for the pdf article on The Background Noise on the HF Amateur Bands

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What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal?
  • Intermodulation distortion.
  • Noise floor.
  • Noise figure.
  • Correct Answer
    Dynamic range.

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

Dynamic range.

For more information, please see the Electronics Notes site for the article What is Noise Floor for radio receivers and also the article Radio Signal to Noise S/N Ratio, SNR and the article What is Noise Figure - measurement & formula

Also, see the High Frequency Electronics site for the article Receiver Sensitivity and Equivalent Noise Bandwidth

For details on the noise, please see the RSGB org site for the pdf article on The Background Noise on the HF Amateur Bands

Last edited by markadlerdallas. Register to edit

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