Technician T3A: How signals fade, bounce and get absorbed
These are the 12 official questions in group T3A 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.
- T3A01Question 1
Why do VHF signal strengths sometimes vary greatly when the antenna is moved only a few feet?
- AThe signal path encounters different concentrations of water vapor
- BVHF ionospheric propagation is very sensitive to path length
- CMultipath propagation cancels or reinforces signals Correct
- DThe Doppler effect causes slight frequency shifts which result in changes in signal strength
Why: Reflected copies of the signal arrive out of step and either cancel or reinforce it, so a few feet makes a big difference.
- T3A02Question 2
How does vegetation affect UHF and microwave signals?
- ACauses knife-edge diffraction, distorting voice peaks
- BAbsorbs signals, leading to poor reception of weak signals Correct
- CAmplifies signals, improving reception of weak signals
- DHas no effect
Why: Leaves and branches absorb UHF and microwave energy, so weak signals get even weaker.
- T3A03Question 3
What antenna polarization is normally used for long-distance CW and SSB contacts on the VHF and UHF bands?
- ARight-hand circular
- BLeft-hand circular
- CHorizontal Correct
- DVertical
Why: Long-distance CW and SSB on VHF/UHF is done with horizontally polarized antennas.
- T3A04Question 4
What is the effect of antenna cross-polarization over a line-of-sight VHF or UHF path?
- AModulation sidebands might become inverted
- BReceived signal strength is reduced Correct
- CSignals have an echo effect
- DNothing significant will happen
Why: If one antenna is vertical and the other horizontal, much less signal gets through.
- T3A05Question 5
When using a directional antenna, how might your station be able to communicate with a distant repeater if buildings or obstructions are blocking the direct line of sight path?
- AChange from vertical to horizontal polarization
- BTry to find a path that reflects signals to the repeater Correct
- CTry the long path
- DIncrease the antenna SWR
Why: A directional antenna aimed at a building or hill can bounce your signal to a repeater you can't reach directly.
- T3A06Question 6
What is the meaning of the term “picket fencing”?
- AAlternating transmissions during a net operation
- BRapid flutter on mobile signals due to multipath propagation Correct
- CA type of ground system used with vertical antennas
- DInterference from cable TV in the form of carriers at fixed intervals across the band
Why: Picket fencing is the rapid flutter on a mobile signal caused by multipath as you move.
- T3A07Question 7
What weather condition might decrease range at microwave frequencies?
- AHigh winds
- BLow barometric pressure
- CPrecipitation Correct
- DColder temperatures
Why: Rain and snow absorb and scatter microwave signals, cutting range.
- T3A08Question 8
What is a likely cause of irregular fading of signals propagated by the ionosphere?
- AFrequency shift due to Faraday rotation
- BInterference from thunderstorms
- CIntermodulation distortion
- DRandom combining of signals arriving via different paths Correct
Why: Signals arriving by several ionospheric paths combine randomly, causing irregular fading.
- T3A09Question 9
Which of the following results from the fact that signals propagated by the ionosphere are elliptically polarized?
- ADigital modes are unusable
- BEither vertically or horizontally polarized antennas may be used for transmission or reception Correct
- CFM voice is unusable
- DBoth the transmitting and receiving antennas must be of the same polarization
Why: Ionospheric signals come back elliptically polarized, so vertical and horizontal antennas both work.
- T3A10Question 10
What effect does multi-path propagation have on data transmissions?
- ATransmission rates must be increased by a factor equal to the number of separate paths observed
- BTransmission rates must be decreased by a factor equal to the number of separate paths observed
- CNo significant changes will occur if the signals are transmitted using FM
- DError rates are likely to increase Correct
Why: Multipath smears the signal, so data error rates go up.
- T3A11Question 11
Which region of the atmosphere can reflect HF radio waves?
- AThe stratosphere
- BThe troposphere
- CThe ionosphere Correct
- DThe electrosphere
Why: The ionosphere reflects (refracts) HF signals back to Earth.
- T3A12Question 12
What effect does fog or rain have on 10-meter and 6-meter band signals?
- AAbsorption
- BLittle effect Correct
- CDeflection
- DIncreased range
Why: At 10 and 6 meters, wavelengths are long enough that fog and rain have little effect.