Practical takeaway
These circuits move information onto a carrier, recover it, or translate the carrier to another frequency.
E7E · Amateur Extra question group
Modulators, Detectors & Mixers
These circuits move information onto a carrier, recover it, or translate the carrier to another frequency.
Amateur Extra exam focus
The explanation below teaches the ideas behind E7E while keeping the important terms recognizable. The Quiz Me button uses the current question-pool wording for this group.
1. A modulator combines information with a carrier
Amplitude, frequency, and phase modulators change the corresponding carrier property according to the information signal. Balanced modulators can suppress the carrier and are common building blocks for SSB generation.
2. Detectors reverse the modulation process
Envelope detectors recover AM, product detectors recover SSB/CW using a local oscillator, and discriminator/phase methods recover FM or phase information. The detector must match the modulation being received.
3. Mixers translate without necessarily demodulating
A mixer produces sum and difference frequencies between its inputs. Receivers and transmitters use filters to select the desired conversion product while suppressing images and spurious products.
E7E checklist
- Modulators impose information on a carrier.
- Detectors/demodulators recover the information.
- Balanced modulators can suppress a carrier.
- Mixers create sum/difference products and require filtering to select the wanted one.
Exam scope: NCVEC 2024-2028 Amateur Extra Class (Element 4), effective July 1, 2024 through June 30, 2028, with February 4, 2026 fourth errata. The current NCVEC pool is the exam authority; explanatory prose here is SPARKA teaching material. NCVEC pool