Belar FMSA-1 FM Digital Stereo Modulation Monitor and Analyzer


Belar FMSA-1


The FMSA-1 is a DSP-based, microprocessor-controlled, FM Stereo Modulation Monitor/ Analyzer. The FMSA-1 digitizes the composite baseband signal and decodes the stereo multiplex portion using digital signal processing techniques. Unlike an analog design, a DSP-based design is immune to variations due to temperature or the aging and tolerance of components. As a result, the FMSA-1 attains superlative performance while requiring virtually no adjustment. By employing linear-phase FIR filters, the FMSA-1 eliminates phase distortion in the recovered audio. This permits unprecedented accuracy in measuring modulation peaks on the Left, Right, L+R and L-R signals. These performance advances result from the mathematically pure demodulation algorithm implemented by the FMSA-1 processors.

All FMSA-1 measurements–peak modulations, injections, and dB ratios–are displayed on digital readouts. The readings can also be viewed remotely on a virtual front panel when the FMSA-1 Digital FM Stereo Monitor/Analyzer is used in conjunction with the Belar Wizard FMMA-1 FM Digital Modulation Monitor/Analyzer and a personal computer. Remote operation of the FMMA-1/FMSA-1 pair in tandem with an automatic audio analyzer facilitates a fully automated stereo proof-of-performance.

The FMSA-1 features user-defined parameters and settings for maximum flexibility. The two UP/DOWN menu keys are used to cycle the 16-digit alphanumeric display to the desired menu; the UP/DOWN parameter keys are then used to select the desired setting. The configuration can be saved to non-volatile memory in the unit in the event of a power loss.


User Interface

When used in combination with the Belar FMMA-1 Wizard and The Wizard Software, the FMSA-1 offers unusual flexibility in remote as well as on-site monitoring. The Wizard Software transforms an ordinary PC into a powerful tool for the real-time graphic display and logging of modulation parameters. When tied to the companion FMMA-1–directly or through modems and a standard phone line–the PC can interrogate and control all functions of the FMSA-1. Passwords allow the restriction of control at three levels.

With the addition of the Belar RFA-4 Frequency Agile FM RF Amplifier to the monitoring system, The Wizard Software permits the remote selection of monitored stations from among 10 preset frequencies or those entered directly by the user. Call letters of preset stations appear on the computer screen for easy identification. Users may also write their own software for controlling and interrogating the FMSA-1 directly through its own RS-232 port.


Total Peak Modulation in Percent or dB
Left Channel Modulation in Percent or dB
Right Channel Modulation in Percent or dB
L + R Modulation in Percent or dB
L – R Modulation in Percent or dB

Pilot Modulation in Percent
Pilot Injection in 0.1 Percent
Direct Reading Separation in dB
Crosstalk in dB
38 kHz Subcarrier Supression in dB
All dB measurements can be made with or without de-emphasis.

Settable Parameters

Hold Time
Time Mode (Real/Past)
Display Hold
Remote Enable
Crosstalk (Direct/Matrix)
75/50 microsecond De-emphasis

Technical Specification

Technical Specification

Input Level
2.8V- 5.7V P-P composite

Input Impedance
100 k , unbalanced, BNC connector
Display: Two large 3 digit 7 segment LED for Left and Right (or L+R and L-R) Modulation 16 segment alphanumeric LED display for menus and parameters

Modulation Display Range
0-127% in 1% increments, accuracy ±0.5%

Pilot Injection Range
0-12.7% in 0.1% increments

Pilot 2V P-P, 500 , unbalanced
Left and Right
Audio (Program) +10 dBm, 600 , balanced
Test 2.5 Vrms, 75  unbalanced
Scope 1.3 Vrms, 75  unbalanced
Digital AES/EBU, 48 kHz

Left to Right 80 dB, 10 Hz to 15 kHz
Right to Left 80 dB, 10 Hz to 15 kHz

L + R to L – R,
L + R to L – R (matrix) 80 dB min
L + R to L – R,
L + R to L – R (direct) 90 dB min
SCA to L + R 90 dB min
SCA to L – R  90 dB min
SCA Interference 90 dB min
Serial Interface RS-232
Unit Interface Wizard Standard Interface

Remote Meter Outputs:
Left Channel Analog Meter,
Right Channel Analog Meter,
Pilot LED, Pilot Relay for interface to Model MP-15 Analog Meter Panel (optional)

Audio Output Specifications
Frequency Response,
Left and Right ±0.05 dB flat, 50 to 15 kHz ±0.25 dB de-emphasized
Signal-to-Noise Ratio, with de-emphasis
Left and Right 90 dB
Harmonic Distortion 0.01% max, 50 to 15 kHz
Intermodulation Distortion 0.01% max (SMPTE)

Dimensions 1 EIA Rack Unit 1.75″H x 14″D x 19″W

Power Requirements  25 watts, 100-240 VAC, 50-60 Hz

Shipping Weight 12 lbs

© Copyright 2000 Belar Electronics Laboratory, Inc. All rights reserved. Specifications subject to change without prior notice.

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

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