Ham Radio Technician Test Equipment & Tools Usage 4 — Questions and Answers
Question 1: What is the advantage of using a PL-259 connector with silver plating instead of a nickel-plated version for HF applications?
- Silver plating increases the connector's weight for stability
- Silver has lower resistance and better RF conductivity than nickel at HF frequencies (Correct answer)
- Silver coating prevents the connector from being used above 30 MHz
- Nickel plating is only suitable for UHF use
Correct answer: Silver has lower resistance and better RF conductivity than nickel at HF frequencies
Silver's higher conductivity reduces skin-effect losses in the connector, which is important even at HF where current concentrates near the conductor surface.
Question 2: A technician notices the receive audio on a mobile radio is distorted only at high volume. What is the most likely cause?
- Antenna SWR is too high
- The audio amplifier is being driven into clipping or the speaker is damaged (Correct answer)
- The squelch threshold is set too low
- The operating frequency is off by 600 Hz
Correct answer: The audio amplifier is being driven into clipping or the speaker is damaged
Distortion at high volume almost always indicates the audio amplifier is overdriven past its linear range or the speaker cone is physically damaged.
Question 3: What does an RF power meter read when the antenna feedline is open (disconnected at the antenna end)?
- Zero watts forward, zero reflected
- Full forward power and full reflected power (SWR infinite) (Correct answer)
- Half forward power and half reflected
- Normal forward power and no reflected
Correct answer: Full forward power and full reflected power (SWR infinite)
An open circuit reflects all transmitted power back toward the transmitter, so forward equals reflected and the SWR reading is effectively infinite.
Question 4: Which type of feedline generally has the lowest loss per 100 feet at VHF frequencies?
- RG-58 coax
- RG-8X coax
- LMR-400 or equivalent low-loss coax (Correct answer)
- Standard TV twin-lead (300 ohm)
Correct answer: LMR-400 or equivalent low-loss coax
LMR-400 and similar large-diameter, foam-dielectric coaxial cables have significantly lower attenuation per unit length than smaller RG-58 or RG-8X at VHF.
Question 5: When using a keyer paddle for CW, what does the 'iambic' mode allow the operator to do?
- Send voice and CW simultaneously
- Squeeze both paddles to automatically alternate dots and dashes (Correct answer)
- Lock the keyer into straight-key mode
- Increase transmit power during fast sending
Correct answer: Squeeze both paddles to automatically alternate dots and dashes
Iambic mode lets the operator squeeze both paddle contacts simultaneously, causing the keyer to automatically alternate between dots and dashes for efficient CW sending.
Question 6: What is the correct way to use a field strength meter during antenna installation?
- Connect it in series with the feedline to measure SWR
- Hold it at a fixed distance and compare relative readings as you adjust the antenna (Correct answer)
- Attach it directly to the transmitter output to calibrate power
- Use it only indoors to avoid external RF interference
Correct answer: Hold it at a fixed distance and compare relative readings as you adjust the antenna
A field strength meter detects radiated RF; by keeping the meter at a consistent distance, relative readings indicate when antenna adjustments improve radiation.
Question 7: What is the purpose of the automatic level control (ALC) circuit in a transceiver?
- It automatically selects the best operating frequency
- It limits the transmitter drive to prevent overdrive and distortion of the final amplifier (Correct answer)
- It adjusts the squelch based on band conditions
- It increases receiver sensitivity during weak signal conditions
Correct answer: It limits the transmitter drive to prevent overdrive and distortion of the final amplifier
ALC senses output power and reduces drive to the final stage when it would otherwise exceed rated levels, protecting the amplifier and preventing distortion.
Ham Radio Technician Test Equipment & Tools Usage 4
What is the advantage of using a PL-259 connector with silver plating instead of a nickel-plated version for HF applications?