Extra exam: amateur practices
Test equipment, receiver performance, noise suppression and interference. 63 questions, 10 at a time, starting with ones you haven't seen.
Rules to remember10 key amateur practices rulesShow the rules
- A spectrum analyzer shows signal amplitude on the vertical axis against frequency on the horizontal axis. (p. 39)
- Spurious signals and intermodulation products appear as separate peaks in frequency, so a spectrum analyzer is the instrument for seeing them. (p. 39)
- SWR can be found with a directional wattmeter (from forward and reflected power), a vector network analyzer, or an antenna analyzer. (p. 40)
- A VNA is calibrated with a short, an open and a precision 50-ohm load, which lets it remove the errors of its cables and connectors. (p. 42)
- A two-port VNA sends a swept signal through a device and measures what comes out, giving a filter's frequency response. (p. 43)
- −174 dBm is the thermal noise in a 1 Hz bandwidth at room temperature (kTB), the floor of a perfect receiver. (p. 44)
- MDS is the minimum discernible signal, the weakest signal a receiver can detect, often set equal to its noise floor. (p. 44)
- Received level = 40 + 6 + 3 − 100 = −51 dBm. (p. 48)
- −100 dBm is 10⁻¹⁰ milliwatt, which is 10⁻¹³ watt, or 0.1 picowatt. (p. 48)
- Arcing in thermostat contacts, a faulty doorbell transformer, or a failing illuminated sign can all cause loud roaring or buzzing interference. (p. 50)
Taken from the explanations to checked practice questions; page numbers link to the official handbook.
Sample amateur practices questions
1.Which of the following is used to measure SWR?
- AAntenna analyzer
- BDirectional wattmeter
- CVector network analyzer
- DAll these choices are correct
Show the answer
✓ D. All these choices are correct
SWR can be found with a directional wattmeter (from forward and reflected power), a vector network analyzer, or an antenna analyzer.
2.Where should a station AC surge protector be installed?
- AOn the single point ground panel
- BOn a ground rod outside the station
- CAt the AC service panel
- DAt an AC outlet
Show the answer
✓ A. On the single point ground panel
Surge protectors should be on the single point ground panel so every protector shares the same ground reference.
3.What is used to suppress radio frequency interference from a line-driven AC motor?
- AA bypass choke in parallel with the motor's field winding
- BA brute-force AC-line filter in series with the motor's power leads
- CA high-pass filter in series with the motor's power leads
- DA bypass capacitor in series with the motor's field winding
Show the answer
✓ B. A brute-force AC-line filter in series with the motor's power leads
A brute-force AC line filter in the motor's power leads blocks RF noise generated by the motor.
4.Which of the following parameters does a spectrum analyzer display on the vertical and horizontal axes?
- ASWR and frequency
- BSWR and time
- CSignal amplitude and time
- DSignal amplitude and frequency
Show the answer
✓ D. Signal amplitude and frequency
A spectrum analyzer shows signal amplitude on the vertical axis against frequency on the horizontal axis.