Technician T7C: Dummy loads, SWR and coax
These are the 11 official questions in group T7C of the 2026–2030 Technician question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- T7C01Question 1
What is the primary purpose of a dummy load?
- ATo prevent transmitting signals over the air when making tests Correct
- BTo prevent over-modulation of a transmitter
- CTo improve the efficiency of an antenna
- DTo improve the signal-to-noise ratio of a receiver
Why: A dummy load absorbs your power so you can test without transmitting over the air.
- T7C02Question 2
Which of the following is used to determine if an antenna is resonant at the desired operating frequency?
- AA VTVM
- BAn antenna analyzer Correct
- CA Q meter
- DA frequency counter
Why: An antenna analyzer shows whether the antenna is resonant at the frequency you want.
- T7C03Question 3
What does a typical RF dummy load consist of?
- AA low-voltage power supply and an AC relay
- BA 50-ohm non-inductive resistor mounted on a heat sink Correct
- CA low-voltage power supply and a DC relay
- DA 50-ohm inductive reactance mounted in a shielded enclosure
Why: A dummy load is a 50-ohm non-inductive resistor mounted on a heat sink.
- T7C04Question 4
What reading on an SWR meter indicates a perfect impedance match between the antenna and the feed line?
- A50:50
- BZero
- C1:1 Correct
- DFull Scale
Why: An SWR of 1:1 means a perfect match.
- T7C05Question 5
Why do most solid-state transmitters reduce output power as SWR increases beyond a certain level?
- ATo protect the RF output amplifier transistors Correct
- BTo comply with FCC rules on spectral purity
- CBecause power supplies cannot supply enough current at high SWR
- DTo lower the SWR on the transmission line
Why: Reducing power at high SWR protects the RF output transistors.
- T7C06Question 6
What does an SWR reading of 4:1 indicate?
- ALoss of -4 dB
- BGood impedance match
- CGain of +4 dB
- DImpedance mismatch Correct
Why: 4:1 SWR means the antenna and feed line impedances don't match.
- T7C07Question 7
What happens to power lost in a feed line?
- AIt increases the SWR
- BIt is radiated as harmonics
- CIt is converted into heat Correct
- DIt distorts the signal
Why: Power lost in a feed line turns into heat.
- T7C08Question 8
Which instrument can be used to determine SWR?
- AVoltmeter
- BOhmmeter
- CIambic pentameter
- DDirectional wattmeter Correct
Why: A directional wattmeter measures forward and reflected power, which gives SWR.
- T7C09Question 9
Which of the following causes failure of coaxial cables?
- AMoisture contamination Correct
- BSolder flux contamination
- CRapid fluctuation in transmitter output power
- DOperation at 100% duty cycle for an extended period
Why: Water getting into coax is the most common cause of failure.
- T7C10Question 10
Why should the outer jacket of coaxial cable be resistant to ultraviolet light?
- AUltraviolet light can increase the resistance of the conductors
- BUltraviolet light can increase losses in the cable’s jacket
- CUltraviolet and RF signals can mix, causing interference
- DUltraviolet light can damage the jacket and allow water to enter the cable Correct
Why: UV light cracks the jacket and lets water into the cable.
- T7C11Question 11
What is an advantage of foam-dielectric versus solid-dielectric coaxial cable?
- AIt is more resistant to moisture contamination
- BIt has higher voltage breakdown
- CIt has less loss per foot Correct
- DIt has a better impedance match to 50 ohms
Why: Foam dielectric has less loss per foot than solid dielectric.