Belar AMMA-2 “The Wizard” Precision DSP Based AM Modulation Monitor/Analyzer



The AMMA-2 is a DSP-based microprocessor-controlled, digital AM modulation monitor/analyzer that precisely measures positive and negative peak modulation, peaks per minute, average peak modulation, modulation density, and more. In addition to monitoring standard AM modulation, the AMMA-2 accurately monitors modulation-dependent carrier level (MDCL) AM transmissions. During MDCL broadcasts, the RF carrier level becomes a dynamic component of the AM signal. The AMMA-2 tracks the carrier, capturing the highest and lowest values of the carrier level, as well as the decibel ratio of the carrier high/low. Modulation readings are referenced to the carrier level appropriate for the MDCL system in use. The optional remote meter panel displays positive modulation, negative modulation, and carrier level simultaneously on three large analog meters.


The AMMA-2 features user-defined parameters and settings for maximum flexibility. Two large UP/DOWN menu keys are used to cycle the 16-character alphanumeric display to the desired menu; the UP/DOWN parameter keys are then used to select the desired setting. The unit configuration may be saved to the on-board non-volatile memory so the settings are retained in the event of a power loss.

A noise menu selection displays rms-detected SNR in decibels (flat or de-emphasized) on the front panel.

A carrier cutoff indicator consisting of three front panel LEDs continuously monitors the approach of negative modulation to carrier cutoff.

A unique “Normal Modulation” indicator shows when modulation is falling within user-defined parameters.

A built-in Audio Sentry audio failure alarm alerts you to loss of modulation or drops in modulation level.

An RS-232/RS-422 port allows the AMMA-2 to be accessed via personal computer. The ASCII command set, documented in the users manual, provides an easy way for users to write their own command and control software. Alternately, the AMMA-2 will be supported in the future by The Wizard Software, which provides unit control and graphing and logging capability for all the AMMA-2 measurements.

A remote alarm connector consisting of 8 pairs of relay contacts provides alarm status information for hard-wired applications. NRSC de-emphasis may be selected internally by moving a jumper plug.


Positive Peak Modulation in Percent
Negative Peak Modulation in Percent
Positive Peaks-per-Minute Count
Negative Peaks-per-Minute Count
Positive Peak Average & Peak Min Modulation
Negative Peak Average & Peak Min Modulation
Positive Average/Peak Modulation Ratio
Negative Average/Peak Modulation Ratio
Normal Modulation Peaks-per-Minute Count
AM Noise rms detected in dB
Carrier Level
Carrier Reference
Carrier High in sliding 1 minute window
Carrier Low in sliding 1 minute window
Carrier Ratio High/Low in dB

Settable Parameters

Positive & Negative Peak Modulation Indicator
Positive & Negative Peaks/Minute Indicator
Normal Modulation Indicator
Positive & Negative Peaks/Minute Duration
Audio Failure Alarm – Time & Modulation
Modulation Mode (Normal/Fixed/MDCL/IMOD)
MDCL Reference
Carrier Shift Alarm
Carrier Failure Alarm – Time & Level
Display Hold Time
Time Mode (Real/Past)
Infinite Hold
Audio Outputs (Test/Meter)
Modulation Calibrator
Tuning Frequency
Tuning Mode (Dir/Auto/Scan/Lock)
Tuning Frequency Increments

In addition to the AMMA-2, Belar has a number of analog remote meter panels for use with Belar AM monitors. The MP-17 Analog Meter Panel is designed for use with the AMMA-2 “The Wizard” AM Modulation Monitor. It features 3 large back-lit meters that continuously display Negative and Positive Modulation and Carrier Level.

Technical Specification

Technical Specification

RF Frequency Range:       
250 kHz to 30 MHz

RF Tuning Increments: 
1 kHz

RF Sensitivity:  
1 to 10 volts rms

RF Input Impedance:    
500 ohm or 50 ohm, internally connected


Display Large:  
Large 3 digit LED for Negative Modulation, 16-character alphanumeric LED display for menus and parameters

Frequency Response:
±0.1 dB, 30 Hz to 10.2 kHz
-3dB @ 11.9kHz
-100 dB @ 16 kHz

Audio Outputs

Audio Monitor: 
+10 dBm, 600 ohm, balanced (XLR), NRSC or Flat

Audio Test:      
2.5 V rms unbalanced (BNC)

Frequency Response:   
±0.1 dB, 30 Hz to 10.2 kHz

less than or equal to 0.1% @ 99% modulation

less than or equal to 0.1% @ 99% modulation

Signal to noise ratio:   
75 dB

Signal Delay Test:
3 ms., Meter: 90 ms.

Automatic Carrier Level Adjustment range:    

Remote Meter Output:    
Jack for optional MP-17 analog remote meter panel

Remote Alarms:   
Relays for Loss of Modulation
Normal, Negative PPM, Positive PPM
Loss of Carrier, Remote, and General alarms.
Relays can be set NO or NC

Serial Interface:

Unit Interface:    
Wizard Standard Interface

Power Requirements:  
20 watts, 100-240 Vac 50/60 Hz

1 3/4″H x 14″D x 19″W (EIA rack mount)

Shipping Weight:   
10 lbs (4.5 kg)

© Copyright 2002 Belar Electronics Laboratory, Inc. All rights reserved.

New in 2015 – 3 Year Factory Warrant to all Belar Products 

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