AM Modulation Calculator

An envelope between 15 V and 5 V means a modulation index of 0.5; with a 100 W carrier the total power is 112.5 W.

Given:

Envelope V_max and V_minModulation index m

V_max (envelope peak):

V_min (envelope trough):

Carrier power P_c (W):

Highest modulating frequency f_m:

Modulation index m =

0.5

Precision

Total power P_c(1 + m²/2): 112.5 W
Power in each sideband P_c m²/4: 6.25 W
Transmission efficiency m²/(2 + m²): 11.11111111 %
Bandwidth 2f_m: 10 kHz
Current ratio Iₜ/I_c = √(1 + m²/2): 1.060660172

Step-by-step solution

m = (V_max − V_min) ÷ (V_max + V_min) = 10 ÷ 20 = 0.5
Pₜ = P_c(1 + m²/2) = 100 × 1.125 = 112.5 W

AM Modulation Formula

m = (V_max − V_min)/(V_max + V_min), Pₜ = P_c(1 + m²/2)

each sideband P_c m²/4; efficiency m²/(2 + m²); bandwidth 2f_m

Worked Example

An AM envelope swinging between 15 V and 5 V on a 100 W carrier with 5 kHz audio:

m = (V_max − V_min) ÷ (V_max + V_min) = 10 ÷ 20 = 0.5
Pₜ = P_c(1 + m²/2) = 100 × 1.125 = 112.5 W

Power in each sideband P_c m²/4: 6.25 W · Transmission efficiency m²/(2 + m²): 11.11111111 % · Bandwidth 2f_m: 10 kHz · Current ratio Iₜ/I_c = √(1 + m²/2): 1.060660172

GATE tip

For several tones, the effective index is m = √(m₁² + m₂² + …). The total-power formula then uses this combined m.

More Communication Calculators

FM Bandwidth Calculator

B ≈ 2(Δf + f_m), β = Δf/f_m

sideband n has amplitude Jₙ(β) of the unmodulated carrier

Example: Broadcast FM with 75 kHz peak deviation and 15 kHz audio: Carson bandwidth = 180 kHz.

Open the fm bandwidth calculator →
PCM Bit Rate Calculator

R = n fₛ × channels

L = 2ⁿ levels; SQNR = 6.02n + 1.76 dB; minimum bandwidth R/2

Example: Telephone-quality speech: 8 bits at 8 kHz, one channel: Bit rate = 64 kbit/s.

Open the pcm bit rate calculator →

Frequently asked questions

Why is AM inefficient?

Even at m = 1 only a third of the power is in the sidebands that carry information; the carrier carries none. DSB-SC and SSB remove the waste.

What happens above m = 1?

Overmodulation: the envelope crosses zero, an envelope detector distorts, and splatter widens the bandwidth.

Sources

The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.

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APA

Scientific Converters. (2026, October 15). AM Modulation Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/am-modulation-calculator/

IEEE

Scientific Converters, "AM Modulation Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/am-modulation-calculator/