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Amateur Radio Quiz: Your Days Are Numbered

04/03/2013

H. Ward Silver, N0AX
n0ax@arrl.net

Worse than the dreaded “word problem,” this April quiz is full of backward problems where I give the answer and you pick the problem. Or something like that. You’ll figure it out!

1) 9
a. The dB equivalent of a power ratio of 4.
b. The number of wavelengths traveled by a 7 MHz signal in 1.29 µs.
c. Value of SWR if a 337.5 Ω load is connected to 75 Ω coaxial cable.
d. Maximum number of ARRL Directors that can fit into W1AW Studio 1 at one time.

2) 622
a. Characteristic impedance of open-wire line with a conductor spacing of 0.5 inches.
b. Maximum number of multipliers for a DX station in the ARRL International DX Contest.
c. Peak-to-peak value of a 220 V RMS ac waveform.
d. Current cost of a genuine Eimac 3-500Z triode in the original shipping carton.

3) 2π/360
a. Conversion factor from degrees to radians.
b. Conversion factor from angular velocity to frequency.
c. Conversion factor between secants and tangents.
d. Conversion factor between hertz and cycles per second.

4) 470 pF
a. Value of capacitance required to resonate with a 3.9 µH inductor at 3.72 MHz.
b. Value of capacitance which creates 338 Ω of reactance at 28 MHz.
c. Value of capacitance exhibited by a one foot length of RG-174 coax.
d. Value of capacitance consumed by over-rotating three-phase del stator.

5) 134 ± 1 percent
a. Brown, red, green, pink
b. Black, orange, yellow, silver
c. Brown, orange, yellow, black, brown
d. Black, R, green dot, J, stripe

6) 225
a. Voltage transformation ratio of a transformer with a turns ratio of 15.
b. Impedance transformation ratio of a transformer with a turns ratio of 5.
c. Impedance transformation ratio of a transformer with a turns ratio of 15.
d. Number of ferrite beads required to suppress RFI from a 160 meter signal.

7) 400
a. Loaded Q of a 10 MHz tuned circuit with a bandwidth of 250 kHz.
b. Loaded Q of a 1 MHz tuned circuit with a bandwidth of 25 kHz.
c. Loaded Q of a 10 MHz tuned circuit with a bandwidth of 25 kHz.
d. Loaded Q of a Field Day operator if coffee is made too strong.

8) 3
a. Length in feet of a 28 MHz 1/4-wave stub of coax with a velocity factor of 0.66.
b. SWR for a reflection coefficient of 0.5.
c. Impedance transformation ratio of a 1/4-wavelength sleeve balun.
d. Number of times to attempt adjustment of a gamma match before calling it “close enough.”

9) 4.6
a. Optimum length of ground radials in electrical degrees at HF.
b. Approximate length in feet of a 1/4-wave ground plane antenna resonant at 50.125 MHz.
c. Approximate length in cm of a 1/2-wave dipole antenna resonant at 222.1 MHz.
d. Apparent weight in kilograms of a hamfest-purchased rotator after being carried all the way back to the car.

10) 30
a. Five time constants for a 100 kΩ bleeder resistor connected across a 60 µF power supply capacitor.
b. The time constant of a 1 MΩ bleeder resistor connected across a 6000 µF power supply capacitor.
c. Peak inverse voltage across a diode in a full-wave bridge rectifier connected to a 6 V RMS secondary.
d. Average number of milliseconds to wait before calling CQ after asking if frequency is in use.

Bonus Question: 90

Answers:
1. b
2. c
3. a
4. a
5. c
6. c
7. c
8. b
9. b
10. a

Bonus Answer: Edition number of the 2013 ARRL Handbook. All of the information necessary to figure out all of these problems is available in any recent edition!

 



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