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Overview

Stereo Encoder/Generator with Limiter

The 8218 is a stand-alone digital FM stereo encoder and limiter that accepts either analog or AES/EBU digital inputs. A transparent digital limiter and overshoot compensator eliminate overshoots introduced by analog or data-compressed digital STLs. When used in a conjunction with OPTIMOD processors, the 8218's encoder introduces no overshoot of its own to ensure maximum signal loudness. Because all processing and encoding is carried out in the digital domain, the 8218's output is stable and artifact-free.

Features

Works with analog or digital STLs.
Works with all analog FM exciters.
Digital limiter/overshoot compensator to assure maximum loudness.
Digital input accepts any sample rate from 32 to 48kHz; reverts to analog input if no valid digital input is present.
Exceptionally clean baseband for a cleaner on-air sound; crosstalk -70dB or better.
Two composite outputs are provided to drive two exciters.
Separation greater than 70dB, 20Hz-15kHz.
Noise less than -90dB, de-emphasized, 100% modulation.
Compact single rack unit.
Front panel LED metering of composite output level, pilot level, left and right input level.
Rear panel DIP switches to control pre-emphasis and limiter settings.

Specifications

System Performance

Frequency Response: Follows standard 50µs or 75µs
Separation: >70dB; 20Hz-15kHz.
Noise (75µs De-emphasized, 100% modulation): <-90dB.
Total System Distortion: 0.02% THD, 0.01% SMPTE IMD, 20Hz-15kHz.
Spectral Protection: 61-100Hz (3dB or less overshoot peak reduction): Overshoot compensator-induced spectral splatter <-80dB.
Crosstalk-Linear (referenced to 100% modulation): <-85dB.
Crosstalk-Non-linear (referenced to 100% modulation): <-85dB.
38kHz Subcarrier Suppression (referenced to 100% modulation): -70dB.
76kHz Subcarrier Sideband (referenced to 100% modulation): <-85dB.
Pilot: 19kHz, ±1Hz, adjustable, 7% to 11% modulation.

Installation Analog Input

Configuration: Left and right.
Impedance: 100k ohms. Termination resistor can be installed.
Common Mode Rejection: >60dB.
Sensitivity: Adjustable to +15dBu to produce 100% modulation.
Maximum Input Level: +18dBu balanced or single-ended.
Connector: XLR-type, female. EMI-suppressed. Pin 1 chassis ground, Pins 2 and 3 are electrically balanced and symmetrical.

Digital Input

Configuration: Two-channel AES/EBU standard.
Sample Rate: Variable, 32kHz to 48kHz, automatically selected.
Sensitivity: -21 to 0dBFS to produce 100% modulation.
Connector: XLR-type.

SCA Subcarrier Inputs

Configuration: Subcarrier inputs sum into composite baseband outputs.
Input Impedance: 600 ohms, unbalanced.
Sensitivity: 0.8Vp-p for 10%, 1.0Vp-p for 12.5% modulation of main carrier.
Maximum Input Level: +18dBu.
Connector: BNC, floating over chassis ground. EMI-suppressed.

Composite Baseband Outputs

Configuration: Two BNC outputs, each with independent Output Level control, output amplifier and connector.
Source Impedance: 0 ohms voltage source or 75 ohms (jumper-selectable).
Load Impedance: 37 ohms or greater. Termination not required.
Level: (0 ohms source impedance, 75 ohms or higher load impedance): Adjustable, 0Vp-p to 8.8Vp-p (100% modulation) with Output Level control.
Connector: BNC, floating over chassis ground. EMI-suppressed.

Pilot Reference Output

Configuration: Buffered square wave reference for RDS or other subcarrier services, TTL level (0 to +5V peak).
Source: TTL level signal. 0 to +5V peak.
Connector: On Remote Control Interface.

AES/EBU Error Flag Output

Source: +15V (On), -15V (Off); 10mA maximum.
Connector: On Remote Control Interface.

Remote Control Interface

Configuration: Seven inputs - select between Analog/Digital Input, Pre-Emphasis On/Off, Operation Mode (Stereo, Mono From Left or Mono From Right).
Voltage: 5-12VAC or DC, momentary or continuous, optically-isolated. Current-limited 10VDC provided to facilitate use of contact closure.
Connector: DB-25, male. EMI-suppressed

Physical

Switches: Input (Analog, Digital), Stereo/Mono (Stereo, Mono L, Mono R), Pilot (On/Off), Crosstalk Test (Operate, Main>Sub, Sub>Main), Meter (Composite, Pilot), Limiter (On/Off).
Screwdriver-Adjustable Controls: Drive (Left, Right and Digital) and Output Levels (Pilot, Comp 1, Comp 2).
Metering: Two 10-segment LED bargraph displays show peak level of Left and Right inputs.
One 10-segment display shows Composite or Pilot output level.
Rear Panel DIP Switch: Selects Pre-emphasis In/Out, Pre-emphasis type (50µs or 75µs), J.17 de-emphasis In/Out, whether or not pre-emphasis and J.17 de-emphasis respond to AES/EBU status bits, digital input level range (four 6dB ranges), and overshoot compensator on/off.
Power Requirements: Switch-selectable on the rear panel, 98-132VAC or 196-264VAC; 89-120VAC for Model 8218/J; 50-60Hz. IEC-standard detachable mains cord supplied. EMI-suppressed.
Fuse: 1|2-amp 3AG 250V Slow-Blow for 115V operation; 1|4-amp "T"-type (250mA) Slow-Blow for 230V operation.
Safety Standards: NRTL-tested to UL Standard 1419, IEC-65 and EN50082-1.
Dimensions: 19" (48.3 cm) wide, 10.25" (26.1 cm) deep, 1 3|4" (4.5 cm) high. 1 rack unit.
Operating Temperature: 32-122°F; 0-50°C.
Humidity: 0-95% RH, non-condensing.
Limited Warranty: One year parts and labor.

Circuit Characteristics Analog-to-Digital Converter

Device: Crystal CS5390.
Performance: 20-bit.

Digital Signal Processing

Device: Motorola DSP56009.
Performance: 24-bit, 144dB internal dynamic range.

Digital-to-Analog Converter

Device: Analog Devices. AD1860.
Performance: 18-bit.

Overshoot Control Limiter

Range: 6dB or more, overshoot compensation and peak limiting.
Overshoot Control at output (input overshoot less than or equal to 4dB): <0.6dB maximum; 0.4dB typical.
Spectral Control (63-100kHz): Splatter caused by Overshoot Limiter <-80dB. Notches protect 19kHz pilot tone and 57kHz RDS spectrum <-80dB.
Circuitry: DSPlockhead algorithm.
Delay Time: 4 milliseconds.

Specifications subject to change without notice.