HamSandwich

Every callsign tells a story. Most of them involve coax.

Study › Amateur Extra › E4C › E4C06

E4C06

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

E4C06E4C →

How much does increasing a receiver's bandwidth from 50 Hz to 1,000 Hz increase the receiver's noise floor?

  1. A3 dB
  2. B5 dB
  3. C10 dB
  4. D13 dB
Why Thermal noise power reaching the detector is proportional to bandwidth, so the noise floor changes by 10 log(B2/B1). Here the ratio is 1000/50 = 20, and 10 log 20 = 13 dB. Note it is 10 log, not 20 log, because we are comparing powers, not voltages.
Watch out The choice of 10 dB would be right only for a 10:1 bandwidth change, such as 100 Hz to 1,000 Hz; 3 dB corresponds to merely doubling the bandwidth.
10 log(bandwidth ratio). 20x wider = 13 dB noisier. Remember 2x=3 dB, 10x=10 dB, so 20x=13 dB.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
← E4C05 All of E4C E4C07 →

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?
RG-213 Coax Cable 75ft with PL259 ConnectorsSponsored · View on Amazon →Diamond X50A Dual Band Base AntennaSponsored · View on Amazon →