BELAR AM MODULATION MONITOR, MODEL AMM-3A
The Belar AMM-3A AM Modulation Monitor is an all-solid-state precision AM demodulator which exceeds the US Federal Communications Commission standards for measuring the total modulation characteristics of medium-frequency AM broadcast transmitters. The detector circuitry of the AMM-3A is non-frequency discriminating, so the unit is suitable for use with shortwave transmitters as well. The AMM-3A employs a unique analog divider circuit which maintains the accuracy of all indications despite changes in carrier level. Simultaneous indications of negative and positive modulation appear on two semi-peak reading meters. Negative and positive modulation peaks are simultaneously indicated on two thumbwheel-programmable peak indicators, as well as individual fixed negative 100% and positive 125% modulation peak indicators. Front-panel pushbuttons select meter indications of relative carrier level and AM noise. The AMM-3A incorporates a carrier-level alarm which indicates when the carrier level falls outside the range required for accurate indications. Also included are an adjustable modulation-level alarm, and a calibration reference to check the accuracy of the readings at any time. An internal jumper can be set to apply the USA NRSC de-emphasis characteristic to the audio outputs.
RF Frequency Range 200 kHz to 50 MHz RF Sensitivity 5 Vrms to 10 Vrms RF Input Impedance 1000 ohm standard, 50 ohm optional RF Input Rear-panel BNC connector Positive Modulation Meter Range 0% to 133% Negative Modulation Meter Range 0% to 100% Accuracy ±2% Peak Modulation Indicators: Negative peak range 1% to 99% in 1% increments Positive peak range 1% to 199% in 1% increments Fixed Indicators -100%, +125% Frequency Response +0.0 dB, -0.5 dB, 20 Hz to 15 kHz Envelope Pulse Response Overshoot <1% Modulation Level Alarm Adjustable threshold, fixed timeout (-15 seconds) Carrier Level Meter Range 0% to 133% Carrier Limit (Loss) Alarm 50% & 133% relative level Audio Monitoring Output +20 dBu (4.9 Vrms), 600 ohm active-balanced Audio Test Output (proof of performance) 2.5 Vrms, rear-panel BNC connector Auxiliary Detector Output 5 Vrms Audio Response +0.0 dB, =0.5 dB, 20 Hz to 15 kHz (detector response -3 dB at 50 kHz) Distortion 0.25% maximum at 99% modulation Signal-to-Noise Ratio >_80 dB (de-emphasis out) AM Noise Level Metering Range -40 dB to -70 dB Remote Outputs: Adjustable negative and positive peak indicators, -100% and +125% peak modulation indicators; positive and negative remote modulation meters, carrier level reference, modulation level alarm, carrier limit (loss) alarm Operating Temperature 0°C to +50°C Power Consumption 8 watts, 100-240 VAC, 50-60 Hz Dimensions 5¼"H x 19"W x 8½" D (EIA rack mount) Shipping Weight 11 lbs. (5 kg)© Copyright 2013 Belar Electronics Laboratory, Inc. All rights reserved. Specifications subject to change without prior notice.
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