Radio Wave Propagation & Modulation Flashcards
7 cards from real Ham Radio Technician Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Radio Wave Propagation & Modulation flashcards as text
What happens to the MUF (Maximum Usable Frequency) when solar activity decreases?
Answer: MUF decreases because the ionosphere is less ionized
Lower solar activity means less UV radiation ionizing the ionosphere, which reduces the MUF and limits long-distance HF propagation to lower frequencies.
What is the purpose of a CTCSS tone on an FM transmission?
Answer: To access repeaters or squelch a receiver only when the correct tone is present
CTCSS (Continuous Tone-Coded Squelch System) is a subaudible tone transmitted to open a repeater's receiver or a radio's squelch only when the matching tone is present.
Why does AM voice occupy more bandwidth than SSB?
Answer: AM transmits both sidebands plus a full carrier, while SSB suppresses one sideband and the carrier
A standard AM signal transmits an upper sideband, a lower sideband, and a carrier, using roughly twice the bandwidth of SSB which transmits only one sideband.
What is multipath propagation?
Answer: Signals arriving at a receiver via two or more different paths, causing interference
Multipath occurs when a transmitted signal reaches the receiver by two or more different routes (e.g., direct path plus a reflected path), which can cause phase cancellation and fading.
At what time of day is the D layer absorption of HF signals greatest?
Answer: Local noon when solar radiation is strongest
The D layer is most heavily ionized at local noon when the sun is at its highest and solar UV radiation is most intense, causing maximum absorption of lower HF frequencies.
What does the term 'skip zone' mean in HF propagation?
Answer: The area where ground wave coverage ends and sky wave coverage begins, with no coverage in between
The skip zone is the region between the farthest reach of ground wave propagation and the nearest point where sky wave signals return to Earth, resulting in no reception of a given station.
Which emission type is most efficient for weak-signal HF communication when bandwidth is limited?
Answer: Single sideband suppressed carrier (SSB)
SSB concentrates all transmitter power into a single sideband with no wasted carrier or duplicate sideband, making it more efficient and narrower than AM or FM for voice.