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E4D02

AMATEUR PRACTICES · Receiver performance characteristics: dynamic range; intermodulation and cross-modulation interference; third-order intercept; desensitization; preselector; sensitivity; link margin

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Which of the following describes problems caused by poor dynamic range in a receiver?

  1. ASpurious signals caused by cross modulation and desensitization from strong adjacent signals
  2. BOscillator instability requiring frequent retuning and loss of ability to recover the opposite sideband
  3. CPoor weak signal reception caused by insufficient local oscillator injection
  4. DOscillator instability and severe audio distortion of all but the strongest received signals
Why Dynamic range is the span between the weakest signal a receiver can detect and the strongest signal it can handle without overload, usually expressed in dB. When that span is too narrow, a strong nearby station drives the front end or mixer into nonlinearity, so its modulation gets transferred onto the desired signal (cross modulation) and the receiver's gain drops on the wanted signal (desensitization), along with mixing products appearing where no real signal exists. These are overload problems, and they appear only when a strong signal is present nearby in frequency.
Watch out The choices mentioning oscillator instability and retuning describe a drifting VFO or synthesizer, which is a frequency stability issue unrelated to how much signal level the receiver can accept; insufficient local oscillator injection degrades mixer conversion gain and noise figure, which is a sensitivity issue.
Dynamic range = strong-signal handling. Symptoms start with strong neighbors: intermod, cross mod, desense. Drift is never the answer here.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of E4D

  1. E4D01 What is meant by the blocking dynamic range of a receiver?
  2. E4D02 Which of the following describes problems caused by poor dynamic range in a receiver?
  3. E4D03 What creates intermodulation interference between two repeaters in close proximity?
  4. E4D04 Which of the following is used to reduce or eliminate intermodulation interference in a repeater caused by a …
  5. E4D06 What is the term for the reduction in receiver sensitivity caused by a strong signal near the received freque…
  6. E4D07 Which of the following reduces the likelihood of receiver desensitization?
  7. E4D08 What causes intermodulation in an electronic circuit?
  8. E4D09 What is the purpose of the preselector in a communications receiver?
  9. E4D10 What does a third-order intercept level of 40 dBm mean with respect to receiver performance?
  10. E4D11 Why are odd-order intermodulation products, created within a receiver, of particular interest compared to oth…
  11. E4D12 What is the link margin in a system with a transmit power level of 10 W (+40 dBm), a system antenna gain of 1…
  12. E4D13 What is the received signal level with a transmit power of 10 W (+40 dBm), a transmit antenna gain of 6 dBi, …
  13. E4D14 What power level does a receiver minimum discernible signal of -100 dBm represent?
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