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E4C03

AMATEUR PRACTICES · Receiver performance: phase noise, noise floor, image rejection, minimum detectable signal (MDS), increasing signal-to-noise ratio and dynamic range, noise figure, reciprocal mixing; selectivity; SDR non-linearity; use of attenuators at low frequencies

E4C03E4C →

What is the term for the suppression in an FM receiver of one signal by another stronger signal on the same frequency?

  1. ADesensitization
  2. BCross-modulation interference
  3. CCapture effect
  4. DFrequency discrimination
Why FM detectors respond to the instantaneous frequency of whatever signal dominates the limiter stage, so when two signals share a channel the stronger one takes over the detector and the weaker one is largely suppressed. This is the capture effect, and only a few dB of difference is usually enough for the stronger station to completely take the channel. It is a property of FM demodulation and is why you rarely hear two FM stations mixed together the way you do with AM or SSB.
Watch out Desensitization is a different problem: a strong signal on a nearby but different frequency drives the receiver front end toward compression and reduces sensitivity to the desired signal. Cross modulation transfers the modulation of a strong signal onto another carrier.
Capture = same frequency, strongest wins. Desense = nearby frequency, everything gets weaker.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
← E4C02 All of E4C E4C04 →

The rest of E4C

  1. E4C01 What is an effect of excessive phase noise in an SDR receiver's master clock oscillator?
  2. E4C02 Which of the following receiver circuits can be effective in eliminating interference from strong out-of-band…
  3. E4C03 What is the term for the suppression in an FM receiver of one signal by another stronger signal on the same f…
  4. E4C04 What is the noise figure of a receiver?
  5. E4C05 What does a receiver noise floor of -174 dBm represent?
  6. E4C06 How much does increasing a receiver's bandwidth from 50 Hz to 1,000 Hz increase the receiver's noise floor?
  7. E4C07 What does the MDS of a receiver represent?
  8. E4C08 An SDR receiver is overloaded when input signals exceed what level?
  9. E4C09 Which of the following choices is a good reason for selecting a high IF for a superheterodyne HF or VHF commu…
  10. E4C10 What is an advantage of having a variety of receiver bandwidths from which to select?
  11. E4C11 Why does input attenuation reduce receiver overload on the lower frequency HF bands with little or no impact …
  12. E4C12 How does a narrow-band roofing filter affect receiver performance?
  13. E4C13 What is reciprocal mixing?
  14. E4C14 What is the purpose of the receiver IF Shift control?
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