Belar: "When accuracy counts, count on Belar"


AMM-2C photo


The Belar AMM-2C Modulation Monitor is a precision, all solid-state AM demodulator designed to measure the modulation characteristics of AM broadcast transmitters over a frequency range of 200 kHz to 50 MHz. The AMM-2C utilizes a unique carrier-referencing system for the peak flasher indications. Peak flasher accuracy, as well as modulation alarm sensitivity, is independent of carrier level over more than a 30% range. A built-in calibrator checks the accuracy of modulation readings. Isolated outputs are provided for the built-in modulation and carrier level alarms. Remote outputs are provided for all modulation indications as well as the carrier level.


  • Separate 100% negative and 125% positive peak modulation indicators
  • Peak indicator, modulation range from 40% to 130%, switchable polarity
  • All peak indicators independent of carrier level
  • Semi-peak-reading modulation meter responds accurately to short duration program peaks
  • Built-in Carrier Level (Loss) and Modulation Level Alarms, both with dry relay contact outputs
  • Built-in Modulation Calibration check
  • Linear-phase detector filter provides accurate modulation indications without overshoot
  • Switchable NRSC audio de-emphasis


    RF Frequency Range              200 kHz to 50 MHz
    RF Sensitivity 			5 Vrms to 10 Vrms
    RF Input Impedance 		1000 ohms std. (50 ohms opt.)
    Modulation Meter Range 	        0 to 133% (switchable to either positive or negative modulation)
    Fixed indicators		-100%, +125%
    Adjustable peak indicator	Range: 40% to 130%
    Modulation Accuracy		 2%
    Envelope Pulse Response		Overshoot <1%
    Modulation Level Alarm		Adjustable threshold, fixed timeout (-15 seconds)
    Carrier Level Deviation
    	Meter Range		 30%
    Carrier Level (Loss) Alarm	Alarms with a 30% drop from nominal carrier level
    Audio Monitoring Output		+10 dBu (2.45 Vrms), 600 ohm, active-balanced
    Audio Test Output 
    	(proof-of-performance)	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)
    Harmonic Distortion		0.25% maximum at 99% modulation
    Signal-to-Noise Ratio		>80 dB (de-emphasis out)
    Remote Outputs:
    	Adjustable, +125%, -100% peak modulation
    	indicators; auxiliary detector, carrier reference,
    	remote modulation meter, remote carrier
    	level meter, modulation level alarm &
    	carrier level (loss) alarm
    Operating Temperature		0C to +50C
    Power Consumption		6 watts, 100-240 VAC, 50-60 Hz
    Dimensions			5"H x 19"W x 7"D
    Shipping Weight			11 pounds (4.5 kg)

    © Copyright 2013 Belar Electronics Laboratory, Inc. All rights reserved. Specifications subject to change without prior notice.

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