Ham Radio General Class Test Digital Modes and Data Communications 2 — Questions and Answers
Question 1: What is the primary function of a TNC (Terminal Node Controller) in a packet radio station?
- It converts computer data to audio tones for radio transmission and decodes received tones back to data (Correct answer)
- It increases the transmitter output power for longer communication range
- It filters adjacent channel interference from neighboring stations
- It monitors band conditions and automatically selects the best operating frequency
Correct answer: It converts computer data to audio tones for radio transmission and decodes received tones back to data
A TNC acts as the interface between a computer and a radio, encoding outgoing data as AFSK audio tones and decoding received audio tones back to digital data.
Question 2: What data link layer protocol is used in traditional amateur packet radio?
- AX.25 (Correct answer)
- TCP/IP
- X.400
- RS-232
Correct answer: AX.25
AX.25 is the amateur radio adaptation of the X.25 protocol, incorporating amateur call signs as station addresses and serving as the foundation of packet radio networking.
Question 3: What is Winlink used for in amateur radio?
- Sending and receiving email messages via radio networks without internet access (Correct answer)
- Linking VHF/UHF repeaters together over the internet
- Monitoring HF propagation beacons and reporting conditions
- Remotely controlling amateur satellites in orbit
Correct answer: Sending and receiving email messages via radio networks without internet access
Winlink is a global radio email system that allows amateur operators to send and receive internet email through HF and VHF radio links, even without any internet connection.
Question 4: What is the approximate bandwidth of an FT8 signal?
- 50 Hz (Correct answer)
- 500 Hz
- 2.7 kHz
- 6 kHz
Correct answer: 50 Hz
An FT8 signal occupies approximately 50 Hz of bandwidth, allowing many simultaneous FT8 signals to coexist within a single 3 kHz SSB passband.
Question 5: Which software application is the primary platform for operating FT8, FT4, WSPR, and other weak-signal modes?
- WSJT-X (Correct answer)
- Fldigi
- Winlink Express
- Ham Radio Deluxe
Correct answer: WSJT-X
WSJT-X, developed by Nobel laureate Joe Taylor (K1JT) and colleagues, is the official software for the entire family of WSJT modes including FT8, FT4, JT65, and WSPR.
Question 6: What is the purpose of forward error correction (FEC) in digital communication modes?
- It allows receivers to detect and correct transmission errors without requesting retransmission (Correct answer)
- It increases the data throughput rate of the digital link
- It reduces the transmitter power required to reach a given distance
- It automatically selects the best digital mode for current band conditions
Correct answer: It allows receivers to detect and correct transmission errors without requesting retransmission
FEC adds redundant data to transmissions so the receiver can reconstruct corrupted bits on its own, improving reliability on noisy HF channels without requiring a repeat request.
Question 7: What is PACTOR primarily used for in amateur radio HF communication?
- High-speed data transfer including email over difficult HF paths (Correct answer)
- Digital voice communication on VHF and UHF bands
- Automatic propagation beacon monitoring and reporting
- Position reporting via satellite uplinks
Correct answer: High-speed data transfer including email over difficult HF paths
PACTOR is a robust HF digital protocol developed for reliable high-speed data transfer including email, widely used by maritime mobile operators and the Winlink network.
Ham Radio General Class Test Digital Modes and Data Communications 2
What is the primary function of a TNC (Terminal Node Controller) in a packet radio station?