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Rice University's 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.^[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.^[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 $A^2{m}^2/(8R)$. 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.^[ref]

A complementary University of Kansas procedure, 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.^[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.

For this single-tone AM model, overmodulation means $m>1$. The signed factor $q(t)$ becomes negative whenever $\cos (\Omega t)<-1/m$. On such intervals,The sign reversal is a $\pi$ radian shift of the carrier's wave phase. At each zero of $q$, the wave envelope vanishes and that phase is undefined. The waveform itself is continuous: the formula has not clipped it or created extra spectral lines.

At $m=1.4=7/5$, sign changes occur at message phases $\Omega t=\arccos (-5/7)$ and $2\pi -\arccos (-5/7)$ within each cycle. At the trough $\Omega t=\pi$, the desired signed factor is $-0.4$, whereas its nonnegative wave envelope is $0.4A$. Ideal envelope recovery followed by subtraction of $A$ would give $-0.6A$ there, rather than the desired message voltage $-1.4A$. This is loss of polarity in the detector, not loss of the message from the full modulated signal. Actual transmitter clipping is a separate signal distortion that can generate additional spectral components.