All 23 Ham Radio Technician questions for T9 Antennas & Feed Lines with the correct answers marked and a short explanation for each, from the official 2026-2030 question pool. Test yourself with the free practice exam.
T9A01
What is a beam antenna?
A. An antenna built from square aluminum beams
B. An omnidirectional antenna invented by Clarence Beam
C. An antenna that concentrates signals in one direction ✓
D. An antenna that focuses the signal into two intense rays
Why: A beam antenna, such as a Yagi, concentrates signals in one direction. This gives gain in that direction and reduces signals from other directions.
T9A02
Which of the following describes a type of antenna loading?
A. Electrically lengthening by inserting inductors in radiating elements ✓
B. Inserting a resistor in the radiating portion of the antenna to make it resonant
C. Installing a spring in the base of a mobile vertical antenna to make it more flexible
D. Strengthening the radiating elements of a beam antenna to better resist wind damage
Why: Loading means electrically lengthening an antenna by inserting inductors (loading coils) in the radiating elements. This lets a physically short antenna resonate at a lower frequency.
T9A03
How is the polarization of an antenna described?
A. By the shape of the driven element
B. By the orientation of the electric field ✓
C. By the orientation of the magnetic field
D. By the direction of radiation
Why: Antenna polarization is described by the orientation of the electric field it radiates. A horizontal antenna produces a horizontally polarized electric field.
T9A04
What is a disadvantage of a handheld radio transceiver’s short flexible antenna compared to a full-sized quarter-wave antenna?
A. It has low efficiency ✓
B. It transmits only circularly polarized signals
C. It is more susceptible to receiver desensitization
D. It only works on analog signals, not digital ones
Why: The short flexible 'rubber duck' antenna on a handheld is much shorter than a quarter wavelength and uses loading to resonate. It is less efficient, radiating less of the power than a full-size quarter-wave.
T9A05
Which of the following increases the resonant frequency of a dipole antenna?
A. Lengthening it
B. Inserting coils in series with radiating wires
C. Shortening it ✓
D. Adding capacitive loading to the ends of the radiating wires
Why: The resonant frequency of a dipole is inversely related to its length. Shortening the dipole raises its resonant frequency, while adding inductive or capacitive loading lowers it.
T9A06
Which of the following types of antennas offers the greatest gain?
A. 5/8 wave vertical
B. Isotropic
C. J pole
D. Yagi ✓
Why: A Yagi is a directional beam antenna that concentrates energy in one direction, giving considerably more gain than a vertical or J-pole. An isotropic antenna is a theoretical reference with zero gain.
T9A07
What is a potential drawback of using a handheld VHF transceiver inside a vehicle that lacks an externally mounted antenna?
A. Signal strength is reduced due to the shielding effect of the vehicle ✓
B. The bandwidth of the antenna will decrease, increasing SWR
C. The SWR might decrease, decreasing the signal strength
D. The handheld will overheat due to reflected power in the vehicle
Why: A car's metal body acts like a shield and blocks much of the RF to and from a handheld used inside it. An external antenna mounted on the vehicle greatly improves signal strength.
T9A08
Why is a 19-inch-long vertical antenna often used on 2 meters?
A. It has high gain
B. It is a resonant half-wave
C. It is a resonant quarter-wave ✓
D. It has low RF radiation exposure
Why: A quarter wavelength at 146 MHz is about (300 / 146) / 4 = 0.51 meters, roughly 20 inches. Trimmed slightly for resonance, it is about 19 inches, a resonant quarter-wave antenna.
T9A09
What is an advantage of a 5/8-wavelength whip antenna for VHF or UHF mobile service compared to a 1/4-wave antenna?
A. It has more gain ✓
B. It radiates at a higher angle
C. It has lower SWR
D. It has lower impedance
Why: A 5/8-wavelength whip concentrates more radiation at low angles toward the horizon than a 1/4-wave whip, giving more gain for mobile VHF and UHF communications.
T9A10
In which direction does a half-wave dipole antenna radiate the strongest signal?
A. Equally in all directions
B. Off the ends of the antenna
C. In the direction of the feed line
D. Broadside to the antenna ✓
Why: A half-wave dipole radiates its strongest signal broadside, at right angles to the wire, and very little off its ends. It is not omnidirectional.
T9A11
What is antenna gain?
A. The additional power that is added to the transmitter power
B. The additional power that is required in the antenna when transmitting on a higher frequency
C. The increase in signal strength in a specified direction compared to a reference antenna ✓
D. The increase in impedance on receive or transmit compared to a reference antenna
Why: Antenna gain is the increase in signal strength in a specified direction compared with a reference antenna, such as a dipole or isotropic. Gain comes from focusing energy, not from adding power.
T9B01
Which of the following connectors should be carefully taped for weather protection when used outdoors?
A. PL259
B. BNC
C. Type N
D. All these choices are correct ✓
Why: PL-259, BNC and Type N connectors can all let water in when used outdoors. Water in a connector increases loss and corrodes the cable, so all should be carefully taped or sealed.
T9B02
What is the most common impedance of coaxial cables used in amateur radio?
A. 8 ohms
B. 50 ohms ✓
C. 600 ohms
D. 12 ohms
Why: Most coaxial cable used in amateur radio has a characteristic impedance of 50 ohms, matching the output of most transmitters. 75-ohm coax is common for TV.
T9B03
Why is coaxial cable the most common feed line for amateur radio antenna systems?
A. It is easy to use and requires few special installation considerations ✓
B. It has less loss than any other type of feed line
C. It can handle more power than any other type of feed line
D. It is less expensive than any other type of feed line
Why: Coax is popular because it is easy to install. It can run near metal, through walls, or underground with few special precautions. Other feed lines such as ladder line can have lower loss.
T9B04
What is the major function of an antenna tuner (antenna coupler)?
A. It matches the antenna system impedance to the transceiver's output impedance ✓
B. It helps a receiver automatically tune in weak stations
C. It allows an antenna to be used on both transmit and receive
D. It automatically selects the proper antenna for the frequency band being used
Why: An antenna tuner, or coupler, transforms the antenna system impedance to match the transceiver's output impedance, usually 50 ohms. This lets the transmitter deliver full power safely. It does not make the antenna itself resonant.
T9B05
What happens as the frequency of a signal in coaxial cable is increased?
A. The characteristic impedance decreases
B. The loss decreases
C. The characteristic impedance increases
D. The loss increases ✓
Why: Coaxial cable loss increases as frequency increases, so the same cable loses more signal at UHF than at HF. Characteristic impedance stays essentially the same with frequency.
T9B06
Which of the following connector types is most suitable as an RF connector for frequencies above 400 MHz?
A. PL-259
B. Type N ✓
C. RS-213
D. DB-25
Why: Type N connectors maintain a constant impedance and are weatherproof, so they perform well above 400 MHz. PL-259 connectors become lossy at UHF and higher, while RS-213 and DB-25 are not RF connectors.
T9B07
Which of the following is true of PL-259 type coax connectors?
A. They are preferred for microwave operation
B. They are watertight
C. They are commonly used at HF and VHF frequencies ✓
D. They are a bayonet-type connector
Why: PL-259 connectors, mating with SO-239 jacks, are common on HF and VHF equipment. They are threaded, not bayonet, are not watertight, and are not suited to microwaves.
T9B08
Which of the following is a source of loss in coaxial feed line?
A. Water intrusion into coaxial connectors
B. High SWR
C. Multiple connectors in the line
D. All these choices are correct ✓
Why: Water intrusion increases loss in the cable, high SWR increases total line loss, and every connector adds a small loss. All these choices are sources of feed line loss.
T9B09
What can cause erratic changes in SWR?
A. Local thunderstorm
B. Loose connection in the antenna or feed line ✓
C. Over-modulation
D. Overload from a strong local station
Why: A loose connection in the antenna or feed line makes the impedance change unpredictably, causing erratic SWR readings. Check connectors and joints when SWR jumps around.
T9B10
What is the electrical difference between RG-58 and RG-213 coaxial cable?
A. There is no significant difference between the two types
B. RG-58 cable has two shields
C. RG-213 cable has less loss at a given frequency ✓
D. RG-58 cable can handle higher power levels
Why: RG-213 is a larger-diameter 50-ohm cable with less loss and higher power handling than thinner RG-58. Both have a single shield.
T9B11
Which of the following types of feed line has the lowest loss?
A. 50-ohm flexible coax
B. Multi-conductor unbalanced cable
C. Air-insulated hardline ✓
D. 75-ohm flexible coax
Why: Air-insulated hardline has the lowest loss because air is a nearly perfect dielectric and the solid outer conductor is very efficient. It is rigid and expensive, so it is used where losses matter most.
T9B12
What is standing wave ratio (SWR)?
A. A measure of how well a load is matched to a transmission line ✓
B. The ratio of amplifier power output to input
C. The transmitter efficiency ratio
D. An indication of the quality of your station’s ground connection
Why: Standing wave ratio (SWR) measures how well a load, such as an antenna, is matched to the transmission line's impedance. An SWR of 1:1 is a perfect match.