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

There is no technical difference in quality — the convention of USB above 10 MHz and LSB below is a universally agreed amateur radio practice for interoperability.

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

Troposcatter uses small irregularities in the troposphere to scatter some signal energy forward, enabling VHF and UHF communication beyond the horizon — typically 100–600 miles.

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

Along the terminator (gray line between day and night), the absorbing D layer rapidly disappears while the F layer remains ionized, creating a brief window of low-loss HF propagation.

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

In PM, phase deviation is proportional to the instantaneous amplitude of the modulating signal; in FM, frequency deviation is proportional to amplitude — but at a given frequency, PM deviation also rises with modulating frequency.

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

At 3.5 MHz, ground wave propagation typically covers 300–500 miles over average terrain, making 80 meters useful for regional communication without relying on the ionosphere.

Ham Radio Technician Test Practice Test

Ham Radio Technician Test Practice Test

Ham Radio Technician Test Radio Wave Propagation & Modulation 5