HAM Radio Extra Class Test Transmitter and Receiver Design Flashcards
6 cards from real HAM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 HAM Radio Extra Class Test Transmitter and Receiver Design flashcards as text
What is the purpose of a speech processor (audio compressor) in an SSB transmitter?
Answer: To increase average transmitted power relative to peak power, improving readability at the receiving end
A speech processor compresses audio peaks, allowing higher average modulation without exceeding peak power limits, which effectively increases the average power and improves intelligibility.
What is the function of a Beat Frequency Oscillator (BFO) or carrier insertion oscillator in a receiver?
Answer: To reinsert the suppressed carrier at the IF for demodulation of SSB and CW signals
The BFO injects a carrier signal at the IF frequency so that SSB and CW signals, which have no carrier of their own, can be properly demodulated.
What is intermodulation distortion (IMD) in a transmitter and what are its effects?
Answer: Distortion products created when two or more signals mix in a nonlinear amplifier stage, generating spurious emissions on adjacent frequencies
IMD occurs when amplifier nonlinearities cause two or more signals to mix, producing spurious products that appear as splatter on frequencies adjacent to the intended transmission.
What is the purpose of a low-pass filter on the output of an HF transmitter?
Answer: To suppress harmonic emissions above the cutoff frequency that could cause interference to other services
A low-pass filter passes the fundamental frequency while attenuating harmonics and other spurious emissions above the cutoff, helping the transmitter meet FCC spurious emission limits.
What happens when an RF power amplifier is insufficiently neutralized?
Answer: The amplifier may oscillate uncontrollably due to feedback from output to input through internal electrode capacitance
Neutralization cancels the unwanted feedback through internal device capacitance; without it, the feedback path can provide enough positive feedback to cause the amplifier to oscillate.
What are the two functions performed by a pi-network output circuit in a tube-type RF power amplifier?
Answer: It provides impedance transformation from the high plate impedance to the 50-ohm antenna load while also acting as a low-pass harmonic filter
The pi-network simultaneously transforms the high impedance of the vacuum tube plate circuit (typically several thousand ohms) to the 50-ohm antenna feed point, and its inherent low-pass characteristic attenuates harmonic content.