Receivers and Transmitters Flashcards
7 cards from real GROL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
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A phase-locked loop (PLL) frequency synthesizer generates output frequencies by:
Answer: Locking a voltage-controlled oscillator to a precise fraction or multiple of a stable reference frequency
The PLL compares the VCO output (divided down) to a stable reference and adjusts the VCO voltage to eliminate phase error, producing precise, synthesized frequencies.
Intermodulation distortion (IMD) in a receiver is produced when:
Answer: Two or more strong signals combine in a nonlinear stage to create spurious in-band products
Nonlinear mixing of two signals (f1 and f2) in a receiver stage generates third-order products at 2f1−f2 and 2f2−f1, which may fall within the IF passband.
The dynamic range of a receiver is best defined as:
Answer: The ratio between the strongest and weakest signals the receiver can handle simultaneously without desensitization or distortion
Dynamic range specifies how large an interfering signal can be relative to a weak desired signal before the receiver's performance is degraded.
Spurious emissions from a transmitter are regulated by the FCC primarily because they:
Answer: Can cause harmful interference to other licensed radio services operating on those frequencies
Spurious emissions radiated on unauthorized frequencies can interfere with other services; FCC rules specify maximum levels in dBc (decibels below carrier).
Selectivity in a receiver refers to its ability to:
Answer: Discriminate between the desired signal and closely spaced interfering signals on adjacent frequencies
Selectivity is determined by the bandwidth and shape factor of IF filters; high selectivity allows the receiver to reject strong adjacent-channel interferers.
Cross-modulation in a receiver occurs when:
Answer: The modulation from a strong interfering signal is transferred onto the desired carrier through a nonlinear stage
A strong interfering signal drives a receiver stage into its nonlinear region, causing the interferer's modulation to appear on the desired carrier.
Overdriving a Class C amplifier with an SSB voice signal causes:
Answer: Splatter — broadband spurious emissions that extend into adjacent channels
Class C amplifiers are nonlinear; flat-topping the SSB peaks generates intermodulation products that spread as wideband splatter across adjacent channels.