Choose the right receiver control for each interference problem and explain what ALC, tuner, TUNE and LOAD do.
Syllabus: Station configuration and operation
Compendium articles on the ideas in this lesson, beyond what the exam asks.
Practise the 13 pool questions for this group. Answers are shuffled, and every one comes with a one-line "why".
| Problem | Control | How it works |
|---|---|---|
| Steady carrier in the passband | Notch filter | cuts a narrow slot at that frequency |
| Neighbour beside a CW signal | Opposite (reverse) sideband | flips the passband so the neighbour falls outside |
| Short impulse noise | Noise blanker | drops gain during each pulse |
| Hiss and general noise | Noise reduction | digital processing; too much distorts the signal |
| Strong signals overloading the receiver | Attenuator | reduces the input before it overloads |
RememberMatch the tool to the interference: carrier, notch. Pulses, blanker. Overload, attenuator.
In a vacuum-tube amplifier, TUNE resonates the output circuit: plate current drops to a pronounced dip exactly where output peaks. LOAD (coupling) then sets output power: raise it to the power you want without exceeding maximum plate current.
RememberTUNE for the dip. LOAD for desired output, within the plate-current limit.
RememberALC limits drive (off for data), delay protects the relay, tuner improves power transfer.
| Feature | Does |
|---|---|
| Electronic keyer | generates dots and dashes automatically for CW |
| Dual VFO | transmit on one frequency, listen on another (split operation) |
Transmit and receive are still never at the same instant: the dual VFO only sets two frequencies.
RememberKeyer makes the dots and dashes. Dual VFO is split: listen here, transmit there.