SCMA-1 FM SCA MODULATION MONITOR

Belar SCMA-1 FM SCA Modulation Monitor Front Panel

Description

The Belar SCMA-1 Digital FM SCA Modulation Monitor and Analyzer is a DSP based precision SCA monitor designed to operate in conjunction with the Belar FMMA-1 or FMM-2 Modulation Monitor or other source of wideband composite.

The SCMA-1 digitizes the composite and decodes the selected subcarrier signal using digital signal processing techniques. Unlike an analog design, a DSP based design is not subject to variations due to temperature, component aging, or component tolerances. The resulting circuit requires no adjustments, but can achieve extremely tight tolerances. In addition, the DSP design allows the use of FIR linear phase filters whose bandwidth can be varied via the front panel. The use of variable bandwidth filters allow the user to optimize the subcarrier BPF and detector LPF cutoff frequencies for a particular SCA modulation scheme. The use of DSP processing also eliminates the need for separate crystal oscillators for each subcarrier frequency, instead all available frequencies are synthesized from a common system clock.

The SCMA-1 implements all its metering and measurement functions using DSP processing. Therefore, the SCMA-1's calibration does not depend on any adjustable circuit components or their tolerances. This guarantees the calibration of the unit will remain stable over time. By digitizing the measurements the user can display modulation peaks, injections, and dB readings directly. As an added benefit, all readings can be viewed remotely using an IBM compatible personal computer.

Features

Specifications

Metering

Total, Main (L+R), Subcarrier Modulation
0-150%, 1% increments, peak reading
Main (L+R), Subcarrier Modulation
+3.5 to -99 dB, 0.5 dB steps, autoranged RMS reading
Subcarrier Injection
0.0-25.5%, 0.1% increments

Subcarrier

Frequency Range
41.0-100.0 kHz, 0.5 kHz steps
BPF Bandwidth
1-16 kHz, 1 kHz steps
Detector Bandwidth
1-8 kHz, 1 kHz steps
Deviation Sensitivities
100% = 1.0-7.0 kHz, 0.1 kHz steps
Internal Calibrator
67 kHz, 6 kHz dev, 1 kHz mod @ 10.0%

Input

Composite
1.0 - 2.0 Vrms (2.8V - 5.7V P-P), 100 kΩ, unbalanced, BNC Connector

Outputs

Main (L+R) Audio
+10 dBm, 600 Ω, balanced, XLR connector
Main (L+R) Test
5 Vrms, 75 Ω, unbalanced, BNC connector
Scope
2.5 Vrms auto-ranged, 75 Ω, unbalanced, BNC connector
Subcarrier Audio
+10 dBm, 600 Ω, balanced, XLR connector
Subcarrier Test
5 Vrms, 75 Ω, unbalanced, BNC connector
Subcarrier BPF
0.1414 Vrms @ 10.0%, 75 Ω, unbalanced, BNC connector

Interface

Serial
RS-232
Unit
Wizard Standard Interface

Remote Meter Outputs

Subcarrier Analog Modulation Meter
Open collector and relay closures for subcarrier presence and subcarrier peak modulation indicators.

Main (L+R) Specifications

20 Hz to 15 kHz

Frequency Response
±0.1 dB
Distortion (THD + Noise)
0.01%
SNR
80 dB

Subcarrier Specifications

BPF BW = 16 kHz, Detector BW = 8 kHz

Frequency Response — BPF In
+0.1, -1.75 dB
Frequency Response — BPF Out
±0.1 dB
Distortion (THD + N) — BPF In
0.25%
Distortion (THD + N) — BPF Out
0.05%
SNR, 150 µsec de-emphasized
80 dB

Frequency response measured from 20 Hz to 8 kHz at 6 kHz deviation. Distortion measured at 1 kHz, 6 kHz deviation.

Crosstalk

Sub to Main
80 dB
Main to Sub
80 dB
Stereo to Sub
80 dB

Packaging

Dimensions
1.75" H × 14.5" D × 19" W, 1 EIA Rack Unit
Power Requirements
17 Watts, 100-240 VAC, 50-60 Hz
Net Weight
7 lbs.
Shipping Weight
11 lbs.

Specifications are subject to change without prior notice.

Downloads

Datasheet

SCMA-1 product overview, features, and specifications,

View Datasheet →

Operator Manual

Complete operating instructions, setup information, controls, connections, and technical information for the SCMA-1.

View Manual →

Software & Updates

Download current SCMA-1 software and review available updates.

Software Updates →