US_GEN
General - Signals and emissions
Signals and emissions groups the G8 section questions for focused review and easier weak-point tracking.
42
Questions
9
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Read the condition in the stem before comparing key terms in the options.
Study rules, calculations, and equipment questions as separate patterns.
After this topic, return to the full pool for mixed practice.
Topic Study Guide
This topic covers signal modulation methods (AM, FM, PM, digital modes), bandwidth calculations, mixing principles, and link budgets. Mastering these concepts is essential for understanding how radio transmitters operate.
High-Yield Checks
- Modulation Types: Distinguish direct FSK from AFSK, and understand Phase Modulation (reactance modulator on an amplifier stage) and Amplitude Modulation (varying instantaneous power).
- Bandwidth Calculations: Memorize Carson's Rule for FM total bandwidth = 2 × (Deviation + Modulating Frequency).
- Mixing and Heterodyning: The local oscillator is varied to convert signals to IF; mixing two RF signals is called heterodyning.
- Link Budget & Margin: Link budget includes transmit power plus antenna gains minus system losses. Link margin is received power minus minimum required signal.
Trap Patterns
- Confusing Phase Modulation (PM) with Frequency Modulation (FM). Note that changing instantaneous frequency is FM, while changing phase angle is PM.
- When calculating FM bandwidth, simply adding deviation and modulating frequency together but forgetting to multiply by 2.
- Misunderstanding "flat-topping" as an ideal state, when it is actually severe signal distortion caused by excessive drive.
- Confusing image response (twice the IF frequency from the desired signal) with intermodulation (odd-order products are closest to original signals).
Review Steps
- Review the definitions and characteristics of basic modulation types (AM, FM, PM, SSB).
- Practice the math for Carson's Rule bandwidth calculations and frequency multiplier deviation division/multiplication.
- Memorize key terms like Heterodyning, Local Oscillator, and Odd-order intermodulation.
- Understand digital modes (like QPSK31, FT8) and their specific modulation techniques (like phase shift keying, 8-tone FSK).
Quick Checks
- What is the formula for calculating FM bandwidth?
- Which order of intermodulation products is closest to the original signal frequencies?
- What type of modulation is produced by a reactance modulator connected to an RF amplifier stage?
- What is the difference between link budget and link margin?
Questions in This Topic
Choose Practice ModeG8A01How is direct binary FSK modulation generated?G8A02What is the name of the process that changes the phase angle of an RF signal to convey information?G8A03What is the name of the process that changes the instantaneous frequency of an RF wave to convey information?G8A04What emission is produced by a reactance modulator connected to a transmitter RF amplifier stage?G8A05What type of modulation varies the instantaneous power level of the RF signal?G8A06Which of the following is characteristic of QPSK31?G8A07Which of the following phone emissions uses the narrowest bandwidth?G8A08Which of the following is an effect of overmodulation?G8A09What type of modulation is used by FT8?G8A10What is meant by the term “flat-topping,” when referring to an amplitude-modulated phone signal?G8A11What is the modulation envelope of an AM signal?G8A12What is QPSK modulation?G8A13What is a link budget?G8A14What is link margin?G8B01Which mixer input is varied or tuned to convert signals of different frequencies to an intermediate frequency (IF)?G8B02What is the term for interference from a signal at twice the IF frequency from the desired signal?G8B03What is another term for the mixing of two RF signals?G8B04What is the stage in a VHF FM transmitter that generates a harmonic of a lower frequency signal to reach the desired operating frequency?G8B05Which intermodulation products are closest to the original signal frequencies?G8B06What is the total bandwidth of an FM phone transmission having 5 kHz deviation and 3 kHz modulating frequency?G8B07What is the frequency deviation for a 12.21 MHz reactance modulated oscillator in a 5 kHz deviation, 146.52 MHz FM phone transmitter?G8B08Why is it important to know the duty cycle of the mode you are using when transmitting?G8B09Why is it good to match receiver bandwidth to the bandwidth of the operating mode?G8B10What is the relationship between transmitted symbol rate and bandwidth?G8B11What combination of a mixer’s Local Oscillator (LO) and RF input frequencies is found in the output?G8B12What process combines two signals in a non-linear circuit to produce unwanted spurious outputs?G8B13Which of the following is an odd-order intermodulation product of frequencies F1 and F2?G8C02Which digital mode is used as a low-power beacon for assessing HF propagation?G8C03What part of a packet radio frame contains the routing and handling information?G8C04Which of the following describes Baudot code?G8C05In an ARQ mode, what is meant by a NAK response to a transmitted packet?G8C06What action results from a failure to exchange information due to excessive transmission attempts when using an ARQ mode?G8C07Which of the following narrow-band digital modes can receive signals with very low signal-to-noise ratios?G8C08Which of the following statements is true about PSK31?G8C09Which is true of mesh network microwave nodes?G8C10How does forward error correction (FEC) allow the receiver to correct data errors?G8C11How are the two separate frequencies of a Frequency Shift Keyed (FSK) signal identified?G8C12Which type of code is used for sending characters in a PSK31 signal?G8C13What is indicated on a waterfall display by one or more vertical lines on either side of a data mode or RTTY signal?G8C14Which of the following describes a waterfall display?G8C15What does an FT8 signal report of +3 mean?G8C16Which of the following provide digital voice modes?