CA_ADV
Advanced - Propagation and operating practice
Propagation and operating practice follows the A-006 section of the Canadian question bank.
55
Questions
6
Sibling Topics
- Pool
- Advanced
- Questions
- 55
- Topic
- Propagation and operating practice
- Region
- CA
Review by section order to build the topic framework first.
For regulatory and safety questions, prefer compliant and conservative actions.
For calculations, check units, multipliers, and approximations.
Topic Study Guide
This topic (A-006) focuses on the core architecture and principles of superheterodyne receivers, covering frequency conversion, intermediate frequency (IF), local oscillators (LO), automatic gain control (AGC), and key performance metrics like sensitivity, selectivity, and noise figure.
High-Yield Checks
- Superheterodyne & Double-Conversion: Superhet design primarily improves selectivity. Double-conversion reduces image interference but increases susceptibility to spurious responses due to extra oscillators.
- Frequency Math: Master the relationship between RF, LO, and IF. The tuned RF frequency is typically the sum or difference of the LO and IF frequencies.
- AGC Mechanics: AGC prevents overload from strong signals by reducing the gain of RF and IF amplifiers. Its behavior is primarily determined by threshold and decay time.
- Noise & Sensitivity: UHF FM sensitivity is often expressed as RF level for 12 dB SINAD. On HF bands, external noise dominates, making extremely low internal noise figures relatively unimportant.
- Detectors & BFO: A product detector mixes an incoming signal with a locally generated carrier. A BFO replaces the suppressed carrier for SSB/CW reception.
Trap Patterns
- Confusing Sensitivity and Selectivity: Sensitivity is the ability to hear weak signals, while selectivity is the ability to reject adjacent frequencies. Do not mix them up.
- Misunderstanding Double-Conversion: Assuming 'double' means twice as loud or twice as sensitive. Its actual core advantage is reducing image interference.
- Misplacing AGC Target Stages: Mistakenly thinking AGC controls audio (AF) amplifiers to adjust volume. It actually targets RF and IF stages to prevent mixer overload.
- Confusing Oscillator and Amplifier Traits: Oscillators must be 'stable and spectrally pure', whereas 'sensitive and selective' describes amplifiers or filters.
Review Steps
- Draw the Receiver Block Diagram: Trace the signal path from the Antenna through the Preselector, RF Amp, Mixer (with LO), IF Amp, Detector (with BFO), to the AF Amp.
- Practice Frequency Math: Use specific values from the bank (e.g., 16 MHz LO and 9 MHz IF) to calculate possible tuned frequencies, checking both sum and difference.
- Compare Performance Metrics: List definitions for Sensitivity, Selectivity, Noise Floor, and SINAD, noting how their importance varies by band (HF vs UHF).
- Understand the AGC Loop: Review why AGC must 'reduce' gain as signal strength increases, and memorize its two key control variables (threshold and decay time).
Quick Checks
- What is the greatest advantage of a double-conversion receiver over a single-conversion one?
- Which two stages in a receiver typically receive the AGC voltage?
- Why is a very low noise figure relatively unimportant for an HF receiver?
- What is the actual function of a product detector in a circuit?
Questions in This Topic
Choose Practice ModeA-006-001-001What are the advantages of the frequency conversion process in a superheterodyne receiver?A-006-001-002What factors should be considered when selecting an intermediate frequency?A-006-001-003One of the greatest advantages of the double-conversion over the single-conversion receiver is that it:A-006-001-004In a communications receiver, a crystal filter would be located in the:A-006-001-005A multiple conversion superheterodyne receiver is more susceptible to spurious responses than a single-conversion receiver because of the:A-006-001-006In a dual-conversion superheterodyne receiver what are the respective aims of the first and second conversion:A-006-001-007Which stage of a receiver has its input and output circuits tuned to the received frequency?A-006-001-008Which stage of a superheterodyne receiver lies between a tuneable stage and a fixed tuned stage?A-006-001-009A single conversion receiver with a 9 MHz IF has a local oscillator operating at 16 MHz. The frequency it is tuned to is:A-006-001-010A double conversion receiver designed for SSB reception has a beat frequency oscillator and:A-006-001-011The advantage of a double conversion receiver over a single conversion receiver is that it:A-006-002-001The mixer stage of a superheterodyne receiver is used to:A-006-002-002A superheterodyne receiver designed for SSB reception must have a beat-frequency oscillator (BFO) because:A-006-002-003The first mixer in the receiver mixes the incoming signal with the local oscillator to produce:A-006-002-004If the incoming signal to the mixer is 3 600 kHz and the first IF is 9 MHz, at which one of the following frequencies would the local oscillator (LO) operate?A-006-002-005The BFO is off-set slightly (500 - 1 500 Hz) from the incoming signal to the detector. This is required:A-006-002-006It is very important that the oscillators contained in a superheterodyne receiver are:A-006-002-007In a superheterodyne receiver, a stage before the IF amplifier has a variable capacitor in parallel with a trimmer capacitor and an inductance. The variable capacitor is for:A-006-002-008In a superheterodyne receiver without an RF amplifier, the input to the mixer stage has a variable capacitor in parallel with an inductance. The variable capacitor is for:A-006-002-009What receiver stage combines a 14.25-MHz input signal with a 13.795-MHz oscillator signal to produce a 455-kHz intermediate frequency (IF) signal?A-006-002-010Which two stages in a superheterodyne receiver have input tuned circuits tuned to the same frequency?A-006-002-011The mixer stage of a superheterodyne receiver:A-006-003-001What is meant by the noise floor of a receiver?A-006-003-002Which of the following is a purpose of the first IF amplifier stage in a receiver?A-006-003-003How much gain should be used in the RF amplifier stage of a receiver?A-006-003-004What is the primary purpose of an RF amplifier in a receiver?A-006-003-005How is receiver sensitivity often expressed for UHF FM receivers?A-006-003-006What is the term used for the decibel difference (or ratio) between the largest tolerable receiver input signal (without causing audible distortion products) and the minimum discernible signal (sensitivity)?A-006-003-007The lower the receiver noise figure becomes, the greater will be the receiver's _________:A-006-003-008The noise generated in a receiver of good design originates in the:A-006-003-009Why are very low noise figures relatively unimportant for a high frequency receiver?A-006-003-010The term which relates specifically to the amplitude levels of multiple signals that can be accommodated during reception is called:A-006-003-011Normally, front-end selectivity is provided by the resonant networks both before and after the RF stage in a superheterodyne receiver. This whole section of the receiver is often referred to as the:A-006-004-001What audio shaping network is added at an FM receiver to restore proportionally attenuated lower audio frequencies?A-006-004-002What does a product detector do?A-006-004-003Distortion in a receiver that only affects strong signals usually indicates a defect in or mis-adjustment of the:A-006-004-004In a superheterodyne receiver with automatic gain control (AGC), as the strength of the signal increases, the AGC:A-006-004-005The amplified IF signal is applied to the ____________ stage in a superheterodyne receiver:A-006-004-006The low-level output of a detector is:A-006-004-007The overall output of an AM/CW/SSB receiver can be adjusted by means of manual controls on the receiver or by use of a circuit known as:A-006-004-008AGC voltage is applied to the:A-006-004-009AGC is derived in a receiver from one of two circuits. Depending on the method used, it is called:A-006-004-010Which two variables primarily determine the behaviour of an automatic gain control (AGC) loop?A-006-004-011What circuit combines signals from an IF amplifier stage and a beat-frequency oscillator (BFO), to produce an audio signal?A-006-005-001What part of a superheterodyne receiver determines the image rejection ratio of the receiver?A-006-005-002What is the term for the reduction in receiver sensitivity caused by a strong signal near the received frequency?A-006-005-003What causes receiver desensitization?A-006-005-004What is one way receiver desensitization can be reduced?A-006-005-005What causes intermodulation in an electronic circuit?A-006-005-006Which of the following is an important reason for using a VHF intermediate frequency in an HF receiver?A-006-005-007Intermodulation interference is produced by:A-006-005-008Which of the following is NOT a direct cause of instability in a receiver?A-006-005-009Poor frequency stability in a receiver usually originates in the:A-006-005-010Poor dynamic range of a receiver can cause many problems when a strong signal appears within or near the front-end bandpass. Which of the following is NOT caused as a direct result?A-006-005-011Which of these measurements is a good indicator of VHF receiver performance in an environment of strong out-of-band signals?