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.
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 k ohms, unbalanced, BNC Connector
Outputs Main (L+R) Audio +10 dBm, 600 ohms, balanced, XLR connector Main (L+R) Test 5 Vrms, 75 ohms, unbalanced, BNC connector Scope 2.5 Vrms auto-ranged, 75 ohms, unbalanced, BNC connector Subcarrier Audio +10 dBm, 600 ohms, balanced, XLR connector Subcarrier Test 5 Vrms, 75 ohms, unbalanced, BNC connector Subcarrier BPF 0.1414 Vrms @ 10.0%, 75 ohms, 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, Det BW = 8 kHz) Frequency Response (20Hz to 8 kHz, 6 kHz Dev) BPF In +0.1, -1.75 dB BPF Out ± 0.1 dB
Distortion (THD + N) @ 1 kHz, 6 kHz dev, 150 µsec BPF In 0.25% BPF Out 0.05%
SNR, 150 µsec de-emphasized 80 dB
Crosstalk Sub to Main 80dB Main to Sub 80dB Stereo to Sub 80dB
Dimensions 1.75"H x 14.5"D x 19"W (1 EIA Rack Unit) Power Requirements 17 Watts, 100-240VAC, 50-60 Hz Net Weight 7 lbs. Shipping Weight 11 lbs.
Printer-friendly version (This is in PDF format and needs to be viewed in Abode Acrobat Reader. If you don't have a copy of the Reader, you can download one for free from Adobe.)
© Copyright 2000 Belar Electronics Laboratory, Inc. All rights
reserved. Specifications subject to change without prior notice.
New | About Us | AM
Equipment | FM Equipment
| TV Equipment | Service
What's New | About Us | AM Equipment | FM Equipment | TV Equipment | Service & Support