Ham Radio Technician Test Radio Wave Propagation & Modulation 5

Question 1

What is the primary advantage of using upper sideband (USB) vs. lower sideband (LSB) on HF?

Accepted Answer

By convention, USB is used above 10 MHz and LSB below 10 MHz, with no technical quality difference

Answer

USB provides better range on all frequencies

Answer

USB eliminates interference from the carrier

Answer

LSB is prohibited on amateur frequencies above 10 MHz

Question 2

What is tropospheric scatter propagation?

Accepted Answer

Scattering of signals by turbulence and irregularities in the troposphere, allowing beyond-horizon VHF/UHF communication

Answer

Refraction of signals by the troposphere's temperature layers

Answer

Reflection of signals off mountain ranges

Answer

Sky wave propagation through the troposhere

Question 3

What causes the 'gray line' to be a favorable time for long-distance propagation on HF?

Accepted Answer

The D layer is absent while the F layer remains ionized, reducing absorption while maintaining refraction

Answer

Atmospheric pressure is lowest at dawn and dusk, reducing signal absorption

Answer

The ionosphere is most stable along the terminator line

Answer

Solar wind is deflected away from the gray line

Question 4

How does phase modulation (PM) differ from frequency modulation (FM)?

Accepted Answer

PM varies the phase of the carrier; FM varies the frequency — PM deviation is proportional to modulating frequency, FM is proportional to amplitude

Answer

PM varies the carrier amplitude; FM varies the carrier frequency

Answer

PM is only used for digital signals; FM is only for voice

Answer

There is no practical difference between PM and FM

Question 5

What is the typical maximum distance for reliable ground wave propagation at 3.5 MHz (80 meters)?

Accepted Answer

300–500 miles

Answer

10–20 miles

Answer

50–100 miles

Answer

1,000–2,000 miles

Question 6

What is meant by the term 'propagation path loss'?

Accepted Answer

The reduction in signal strength as a radio wave travels from transmitter to receiver

Answer

Loss caused only by ionospheric absorption

Answer

The loss of signal when transmitted through a coaxial cable

Answer

Attenuation caused by antenna mismatch

Question 7

Which phenomenon explains why 6-meter (50 MHz) signals can sometimes propagate across the entire continental US without the F layer?

Accepted Answer

Sporadic-E propagation

Answer

Tropospheric ducting

Answer

Meteor scatter

Answer

Ground wave