= Amplitude modulation laboratory
Rice University's \i[ELEC 332: In the Lab] makes the model experimentally testable. Preparation resets the <spectrum analyzer> and observes an unmodulated generator output on it and an <oscilloscope>. A Wavetek <function generator> supplies external modulation. The specified $10\,\mathrm{MHz}$ carrier and $10\,\mathrm{kHz}$ message separate three peaks. Marker readouts give <frequency> and level; narrowing resolution bandwidth shows how the instrument broadens a line.<ELEC 332: In the Lab, Rice University>[ELEC 332: In the Lab, Part 1, “Initial Configuration”, “Initializing”, “Observing a signal”, “Changing the bandwidth”, “Using the marker” and “Resolving signals”]{ref}
Part 3 uses an SA602 <analog multiplier> module. The message generator also triggers the <oscilloscope>; multiplier output feeds both displays. A no-offset module supplies a suppressed-carrier control. Replacing it with the offset-adding module restores the carrier; varying levels tests <signal distortion>. Finally a radio receives the conventional <AM> transmission, and varying message <frequency> checks that the heard tone belongs to this source. These are prescribed observations, not reported measurements.<ELEC 332: In the Lab, Rice University>[ELEC 332: In the Lab, Part 3, module descriptions and “Connect the components” through “AM transmitter”: input/output connections, offset control, level sweep and receiver check]{ref}
Calibration matters: verify generator voltage at the connected input, distinguish peak from <peak-to-peak amplitude> and <root mean square>, and check analyser units and loading before comparing heights with $Am/2$ or <power> with $A^2m^2/(8R)$. The unmodulated carrier is a reference control. Limited resolution can merge sidebands; generator harmonics can add peaks. Rice explicitly demonstrates both limitations in Part 1.<ELEC 332: In the Lab, Rice University>[ELEC 332: In the Lab, Part 1, “Resolving signals”: message-generator harmonic distortion and unresolved sidebands when the message frequency is reduced]{ref}
A complementary University of Kansas procedure, \i[A.2 - Amplitude Modulation], calibrates the added carrier and the suppressed-carrier product separately to $4\,\mathrm V$ peak-to-peak before recombining them. It holds the carrier fixed, varies modulation depth, reads envelope extrema and carrier-to-sideband <power> differences, then connects the demodulator and adjusts its tunable <low-pass filter> for recovery, comparing the output with the message. These are setup targets and comparison instructions, not measured results.<A.2 - Amplitude Modulation, University of Kansas EECS 562>[A.2 - Amplitude Modulation, §§A.2.5–A.2.8, printed pp. A.2.4–A.2.5 (PDF pp. 4–5), Figures A.2.3–A.2.4 and steps A.2.6(iv–xiv), A.2.8(i–vii): separate level calibration, fixed-carrier sweep and demodulation comparison]{ref}
The inference combines time and <frequency spectrum> readouts: correct sideband spacing tests frequency translation, relative heights test modulation depth, and the recovered message tests the detector. Hardware clipping, receiver filtering and <noise> can spoil recovery even at $m<1$. Conversely failure of an <envelope detector> at $m>1$ does not demonstrate failure of a synchronized multiplier receiver. The two diagrams above illustrate the stipulated linear model only.
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