Orban 8218 User manual

Operating Manual
Digital
FM Stereo
Encoder/Generator
with Limiter
Model 8218

IMPORTANT NOTE: Refer to the unit’s rear or side panel for your Model #.
Model Number: Description:
8218/U
8218/E
82 18Stereo Encoder,
set to 115V (for 98- 132V operation),
switchable to 50ns or 75ns.
8218 Stereo Encoder,
set to 230V (for 196-264V operation),
switchable to 50ns or 75ns.
Manual:
Part Number:
96082-000-02
Description:
8218 Manual
CAUTION: TO REDUCE THE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER (OR BACK).
NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRICAL SHOCK,
DO NOT EXPOSE THIS APPLIANCE TO RAIN OR MOISTURE.
This symbol, wherever it appears,
alerts you to the presence of uninsulated
dangerous voltage inside the enclosure —voltage
that may be sufficient to constitute arisk of shock.
This symbol, wherever it appears,
alerts you to important operating and
maintenance instructions in the accompanying
literature. Read the manual.

IMPORTANT SAFETY INSTRUCTIONS
All the safety and operating instructions should be read before the appliance is operated.
Retain Instructions: The safety and operation instructions should be retained for future reference.
Heed Warnings: All warnings on the appliance and in the operating instructions should be adhered to.
Follow Instructions: All operation and user instructions should be followed.
Water and Moisture: The appliance should not be used near water (e.g., near abathtub, washbowl, kitchen sink, laundry tub, in awet
basement, or near aswimming pool, etc.).
Ventilation: The appliance should be situated so that its location or position does not interfere with its proper ventilation. For example, the
appliance should not be situated on abed, sofa, rug, or similar surface that may block the ventilation openings; or, placed in abuilt-in
installation, such as abookcase or cabinet that may impede the flow of air through the ventilation openings.
Heat: The appliance should be situated away from heat sources such as radiators, heat registers, stoves, or other appliances (including
amplifiers) that produce heat.
Power Sources: The appliance should be connected to apower supply only of the type described in the operating instructions or as
marked on the appliance.
Grounding or Polarization :Precautions should be taken so that the grounding or polarization means of an appliance is not defeated.
Power-Cord Protection: Power-supply cords should be routed so that they are not likely to be walked on or pinched by items placed
upon or against them, paying particular attention to cords at plugs, convenience receptacles, and the point where they exit from the appliance.
Cleaning: The appliance should be cleaned only as recommended by the manufacturer.
Non-Use Periods: The power cord of the appliance should be unplugged from the outlet when left unused for along period of time.
Object and Liquid Entry: Care should be taken so that objects do not fall and liquids are not spilled into the enclosure through
openings.
Damage Requiring Service: The appliance should be serviced by qualified service personnel when:
The power supply cord or the plug has been damaged; or
Objects have fallen, or liquid has been spilled into the appliance; or
The appliance has been exposed to rain; or
The appliance does not appear to operate normally or exhibits amarked change in performance; or
The appliance has been dropped, or the enclosure damaged.
Servicing: The user should not attempt to service the appliance beyond that described in the operating instructions. All other sen/icing
should be referred to qualified service personnel.
The Appliance should be used only with acart or stand that is recommended by the manufacturer.
Safety Instructions (European)
Notice For U.K. Customers If Your Unit Is Equipped With APower Cord.
WARNING: THIS APPLIANCE MUST BE EARTHED.
The cores in the mains lead are coloured in accordance with the following code;
GREEN and YELLOW -Earth BLUE -Neutral BROWN -Live
As colours of the cores in the mains lead of this appliance may not correspond with the coloured markings identifying the terminals in your
plug, proceed as follows:
The core which is coloured green and yellow must be connected to the terminal in the plug marked with the letter E, or with the earth symbol,
(A), or coloured green, or green and yellow.
The core which is coloured blue must be connected to the terminal marked Nor coloured black.
The core which is coloured brown must be connected to the terminal marked Lor coloured red.
AThe power cord is terminated in aCEE7/7 plug (Continental Europe). The green/yellow wire is connected directly to the unit's chassis. If
you need to change the plug and if you are qualified to do so, refer to the table below.
WARNING: If the ground is defeated, certain fault conditions in the unit or in the system to which it is connected can result in full line
voltage between chassis and earth ground. Severe injury or death can then result if the chassis and earth ground are touched simultaneously.
CONDUCTOR WIRE COLOR
Normal Alt
LLIVE BROWN BLACK
NNEUTRAL BLUE WHITE
EEARTH GND GREEN-YELLOW GREEN
AC Power Cord Color Coding

Safety Instructions (German)
Gerat nur an der am Leistungsschild vermerkten Spannung und Stromatt betreiben.
Sicherungen nur durch solche, gieicher Stromstarke und gleichen AbschaJtverhaltens ersetzen. Sicherungen nie uberbrucken.
Jedwede Beschadigung des Netzkabels vermeiden. Netzkabel nicht knicken Oder quetschen. Beim Abziehen des Netzkabels den
Stecker und nicht das Kabel enfassen. Beschadigte Netzkabel sofort auswechseln.
Gerat und Netzkabel keinen ubertriebenen mechanischen Beaspruchungen aussetzen.
Um Beruhrung gefahriicher elektrischer Spannungen zu vermeiden, dart das Gerat nicht geoffnet werden. Im Fall von Betriebsstorun-
gen dart das Gerat nur Von befugten Servicestellen instandgesetzt werden. Im Gerat befinden sich keine, durch den Benutzer
reparierbare Teile.
Zur Vermeidung von elektrischen Schlagen und Feuer ist das Gerat vor Nasse zu schutzen. Eindringen von Feuchtigkeit und
Flussigkeiten in das Gerat vermeiden.
Bei Betriebsstorungen bzw. nach Eindringen von Flussigkeiten Oder anderen Gegenstanden, das Gerat sofort vom Netz trennen und
eine qualifizierte Servicestelle kontaktieren.
Safety Instructions (French)
On s’assurera toujours que la tension et la nature du courant utilise correspondent bien aceux indiques sur la plaque de I’appareil.
N’utiliser que des fusibles de meme intensity et du meme principe de mise hors circuit que les fusibies d’origine. Ne jamais shunter les
fusibles.
Eviter tout ce qui risque d’endommager le cable seceur. On ne devra ni le plier, ni I’aplatir. Lorsqu’on d6branche I’appareil, tirer la fiche
et non le cable. Si un cable est endommage, le remplacer imm6diatement.
Ne jamais exposer I’appareil ou le cable aune contrainte mecanique excessive.
Pour eviter tout contact averc une tension electrique dangereuse, on n’oouvrira jamais I’appareil. En cas de dysfonctionnement,
I’appareil ne peut etre repare que dans un atelier autorise. Aucun element de cet appareil ne peut etre repare par I’utilisateur.
Pour eviter les risques de decharge electrique et d'incendie, proteger 1‘appareil de I’humidite. Eviter toute penetration d’humidite ou fr
liquide dans I’appareil.
En cas de dysfonctionnement ou si un liquide ou tout autre objet apenetre dans I’appareil couper aussitot I’appareil de son alimentation
et s’adresser aun point de service apresvente autorise.
Safety Instructions (Spanish)
Hacer funcionar el aparato solo con la tension yciase de coniente senaladas en la placa indicadora de caracteristicas.
Reemplazar los fusibles solo por otros de la misma intensidad de coniente ysistema de desconexion. No poner nunca los fusibles en
puente.
Proteger el cable de alimentacion contra toda ciase de danos. No doblar oapretar el cable. Ai desenchufar, asir el enchufe yno el
cable. Sustituir inmediatamente cables danados.
No someter el aparato yel cable de alimentacion aesfuerzo mecanico excesivo.
Para evitar el contacto con tensiones el§ctricas peligrosas, el aparato no debe abrirse. En caso de producirse fallos de funcionamiento,
debe ser reparado solo portalleres de servicio autorizados. En el aparato no se encuentra ninguna pieza que pudiera ser reparada por
el usuario.
Para evitar descargas electricas eincendios, el aparato debe protegerse contra la humedad, impidiendo que penetren esta oliquidos
en el mismo.
En caso de producirse fallas de funcionamiento como consecuencia de la penetracion de liquidos uotros objetos en el aparato, hay
que desconectarlo inmediatamente de la red yponerse en contacto con un taller de servicio autorizado.
Safety Instructions (Italian)
Far funzionare I'apparecchio solo con la tensione eil tipo di corrente indicati sulla targa riportante idati sulle prestazioni.
Sostituire idispositivi di protezione (valvole, fusibili ecc.) solo con dispositivi aventi lo stesso amperaggio elo stesso comportamento di
interruzione. Non cavallottare mai idispositivi di protezione.
Evitare qualsiasi danno al cavo di collegamento alia rete. Non piegare oschiacciare il cavo. Per staccare il cavo, tirare la presa emai
il cavo. Sostituire subito icavi danneggiati.
Non esporre I’apparecchio eil cavo ad esagerate sollecitazioni meccaniche.
Per evitare il contatto con le tensioni elettriche pericolose, I'apparecchio non deve venir aperto. In caso di anomalie di funzionamento
I’apparecchio deve venir riparato solo da centri di servizio autorizzati. Nell’apparecchio non si trovano parti che possano essere riparate
dall’utente.
Per evitare scosse elettriche oincendi, I’apparecchio va protetto dall’umidita. Evitare che umidita oliquidi entrino nell’apparecchio.
In caso di anomalie di funzionamento rispettivamente dopo la penetrazione di liquidi ooggetti nell’apparecchio, staccare immedi-
atamente I'apparecchio dalla rete econtattare un centro di servizio qualificato.

Operating Manual
Digital
FM Stereo
Encoder/Generator
with Limiter
Model 8218

WARNING
This equipment generates, uses, and can radiate radio-frequency energy. If it is not
installed and used as directed by this manual, it may cause interference to radio
communication. This equipment complies with the limits for aClass Acomputing
device, as specified by FCC Rules, Part 15, Subpart J, which are designed to provide
reasonable protection against such interference when this type of equipment is oper-
ated in acommercial environment. Operation of this equipment in aresidential area is
likely to cause interference. If it does, the user will be required to eliminate the
interference at the user's expense.
WARNING
‘This digital apparatus does not exceed the Class Alimits for radio noise emissions
from digital apparatus set out in the Radio Interference Regulations of the Canadian
Department of Communications.” “Le present appareil numerique n’emet pas de bruits
radioelectriques depassant les limites applicables aux appareils numeriques (de las
class A) prescrites dans le Reglement sur le brouillage radioelectrique edicte par le
ministers des Communications du Canada.”
IMPORTANT
Perform the installation under static control conditions. Simply walking across arug can
generate astatic charge of 20,000 volts. This is the spark or shock you may have felt when
touching adoorknob or some other conductive item. Amuch smaller static discharge is likely to
completely destroy one or more of the CMOS semiconductors employed in this product. Static
damage will not be covered under warranty.
There are many common sources of static. Most involve some type of friction between two
dissimilar materials. Some examples are combing your hair, sliding across aseat cover or
rolling acart across the floor. Since the threshold of human perception for astatic discharge is
3000 volts, many damaging discharges will not even be noticed.
Basic damage prevention consists of minimizing generation, discharging any accumulated
static charge on your body or work station and preventing that discharge from being sent to or
through an electronic component. Astatic grounding strap (grounded through aprotective
resistor) and astatic safe workbench with aconductive surface should be used. This will prevent
any buildup of damaging static.
Patents pending.
Orban and Hadamard Transform Baseband Encoder are registered trademarks.
All trademarks are property of their respective companies.
This manual is part number 96082-000-02
Printed 10/98
©Copyright 1998 Orban, Inc.
orban
1525 Alvarado Street, San Leandro, CA 94577 USA
Phone: [phone] Fax: [phone] E-mail: [email protected]

Orban
8218 Digital FM Stereo
Encoder/Generator
with Limiter
Operating Manual
page contents
1-
1Section 1:Introduction
821 8Digital Stereo Encoder/Generator with Limiter
Input/Output Configurations
Remote Control Interface
Location of 821
8
Line-Up Facilities
2-
1Section 2:Installation
Installation of 821
8
System Setup
3-
1Section 3:Operation
821 8Controls and Meters

8218 Digital Stereo Encoder INTRODUCTION
Section 1
Introduction
page contents
1-2 Figure 1-1: Front
1-3 8218 Digital FM Stereo Encoder
1-4 Input/Output Configurations
1-4 Analog Left/Right Inputs
1-4 Digital AES/EBU Left/Right Input
1-5 Composite Baseband Outputs
1-5 Subcarriers
1-6 AES/EBU Error Alarm Function
1-6 Remote Control Interface
1-6 Location of 8218
1-6 Optimal Control of Peak Modulation Levels
1-8 Transmission from Studio to Transmitter
1-8 Digital links
1-9 Video microwave STLs with PCM adapter
1-9 Analog land line (PTT/post office line)
1-9 Dual microwave STLs
1-10 Line-Up Facilities
1-10 Left/Right Input Level
1-10 Composite Output Level
1-10 Pilot Injection Metering
1-11 Figure 1-2: J.17 De-Emphasis Curve

INTRODUCTION Orban Model 821
8
Figure 1:Front

8218 Digital Stereo Encoder INTRODUCTION
8218 Digital FM Stereo Encoder
More and more FM stations are transporting their audio digitally, from studio to transmitter.
However, digital links typically handle left/right rather than composite. Orban’s 8218
Digital FM Stereo Encoder can extend your all-digital performance through to the stereo
encoder. It’s designed to perfectly complement Orban’s OPTIMOD-FM digital audio
processors in an all-digital transmission system.
All encoding is done entirely in the digital domain by adedicated DSP chip, producing two
analog composite outputs with outstanding specifications and long-term stability. The 8218
accepts either analog or AES/EBU digital inputs. The digital input automatically synchro-
nizes to and de-jitters any standard incoming sampling rate. In addition, it responds to status
bits in the AES/EBU data stream that may be used to turn de-emphasis on or off. This feature
allows automatic switching of pre-emphasis and/or J.17 (NICAM) de-emphasis to accom-
modate different transmission schemes.
An Overshoot Control Limiter can be applied to the incoming audio, limiting overshoots to
less than 0.5dB while introducing minimal (or no) audible artifacts and without contaminat-
ing the baseband spectrum above 57kHz. The Overshoot Control Limiter is particularly
useful if the processed audio has been passed to the 8218 through adigital STL that uses
lossy encoding, like MPEG, Dolby, or APT-X. The Overshoot Control Limiter uses
lookahead techniques, and, when activated, adds atime delay of 4milliseconds to the stereo
encoding process.
Features
•>70dB separation, 20Hz- 15kHz.
•<-90dB noise and distortion (after de-emphasis, and referenced to 100% modu-
lation output).
•Digitally-created composite signal, from either analog or AES/EBU digital input.
The 8218 also accepts two analog SCA inputs, and sums them with analog
composite output. The analog composite appears on two outputs, each with
individual level control.
•Built-in sample rate converter that allows 8218 to accept any digital AES/EBU
input sample rate between 32kHz and 48kHz.
•Recessed front panel controls for selecting Input type (Analog/Digital), Ste-
reo/MonoL/MonoR mode, Pilot On/Off, and Crosstalk Tests.
•Front panel metering of Left and Right inputs plus Composite or Pilot outputs.
•Recessed front panel multi-tum screwdriver potentiometers for Analog Left,
Analog Right, and Digital input levels, as well as for Pilot, Composite #1, and
Composite #2 output levels.
•Recessed rear panel DIP switch for selecting pre-emphasis In/Out, pre-emphasis
type (50ps/75(J.s), J.17 de-emphasis In/Out, and whether or not the stereo en-
coder’s pre-emphasis and J.17 de-emphasis settings respond to status bits of the

INTRODUCTION Orban Model 8218
AES/EBU digital input, Overshoot Control Limiter in/out, and AES/EBU input
range.
•Remote (contact closure) interface using opto-isolation has pins to select between
analog or digital input, turn pre-emphasis on or off, and to select among stereo,
mono from left, or mono from right operational modes. Also on the remote
connector is adigital pilot reference output clock for external subcarrier gener-
ators like RDS. This is aTTL level signal with 0to +5V transition occurring at
the pilot zero crossing.
•Overshoot Control Limiter limits overshoot to less than 0.5dB with minimum
artifacts.
•AES/EBU error alarm function provides an alarm that indicates if afaulty
AES/EBU signal is being received at the 821 8’s digital input.
Input/Output Configurations
The 8218 provides:
•Analog left/right inputs or digital AES/EBU left/right input.
•Composite baseband outputs.
•SCA subcarrier inputs.
•Pilot Reference output.
•AES/EBU error alarm function.
Analog Left/Right Inputs
The left and right analog inputs are on XLR-type female connectors on the rear panel. Input
impedance is greater than lOOkQ; balanced and symmetrical. Inputs can accommodate from
0to +15dBu for 100% modulation. (OdBu =0.775Vrms).
Level control of the analog inputs is via the screwdriver-adjustable Left and Right Drive
controls, located on the 8218’s front panel.
The Left/Right meter on the 8218 shows input levels as a10-segment bar graph (5 to 110%).
100% is the threshold of the built-in Overshoot Control Limiter. Inputs reading below 100%
on this meter are unaffected.
Digital AES/EBU Left/Right Input
The digital input follows the professional AES/EBU standard. The left/right digital input is
on one XLR-type female connector on the rear panel.
The digital input can accommodate a20dB level adjustment, in four 6dB ranges. Fine level
control of the AES/EBU input is via the screwdriver-adjustable Digital Drive control, located

8218 Digital Stereo Encoder INTRODUCTION
on the 821 8’ sfront panel. Input level range select is via DIP switches located on the 821 8’
s
rear panel.
The 82 18accepts any digital AES/EBU input sample rate between 32kHz and 48kHz by use
of abuilt-in sample-rate converter.
The 8218 can be switched between digital and analog inputs by the front panel Input select
switch or by remote interface. Both analog and digital outputs are active continuously.
Composite Baseband Outputs
The stereo encoder has two unbalanced baseband outputs (Composite 1and Composite 2)
on two BNC connectors on the rear panel. Each output can be strapped for OQ or 750 source
impedance (jumper-selectable), and can drive up to 8.8V peak-to-peak into 750 in parallel
with up to 0.047pF (100ft/30m of RG-59/U cable) before any noticeable performance
degradation occurs. (The 8218 is shipped from the factory with OO source impedance.)
Level control of each output is via aseparate screwdriver control accessible from the front
panel.
Aground lift switch is available on the rear panel. This can prevent ground loops between
the 8218 and the transmitter.
The Composite meter on the 8218shows composite output levels as a10-segment bar graph
(5% to 110%). The sensitivity of this meter changes when the Overshoot Control Limiter is
activated. If the Overshoot Control Limiter is defeated, applying asinewave equally to both
left and right inputs such that the two input meters read 100% will cause the Composite
meter to read 100%, provided that the pilot tone is ON and set to 9% injection. Activating
the Overshoot Control Limiter reduces the sensitivity of the Composite meter by 4%,
allowing amargin such that the Overshoot Control Limiter meter will normally read 100%
on program peaks.
The Overshoot Control Limiter has aslight residual overshoot (less than
0.5dB) because, unlike a simple clipper, it controls its output spectrum very
tightly. The non-linear filtering necessary to accomplish this causes a small
amount of uncertainty in the peak output level. While the Overshoot
Control Limiter uses lookahead techniques to minimize this uncertainty,
these techniques cannot entirely eliminate it without introducing some
audible gain pumping, which we considered unacceptable. We therefore
designed the circuit for maximum audible transparency at the cost of a
small amount of overshoot.
You ordinarily adjust the 8218’s output level so that 100% corresponds to ±75kHz carrier
deviation. Note that if you apply subcarriers (SCAs) to the rear panel subcarrier input, the
meter will read higher than 100%. For example, in the U.S.A., if two subcarriers are used,
the meter will usually read peaks of 110%, corresponding to ±82.5kHz deviation.
Subcarriers
The 8218 has two unbalanced lOkQ subcarrier (SCA) inputs with Rear-panel BNC connec-
tors to accept any subcarrier at or above 23kHz. The subcarrier will be mixed into each
composite output, and its level will be affected by the composite level control for that output.

INTRODUCTION Orban Model 8218
The gain is scaled so that 0.8V peak-to-peak at the subcarrier input produces 10% subcarrier
injection with reference to 100% deviation of the FM carrier.
A19kHz TTL-level square wave is available on pin 24 of the remote interface, located on
the rear panel of the unit. This provides ameans for synchronizing an external subcarrier
generator, like an RDS (Radio Data Systems) subcarrier, to the 19kHz pilot tone.
AES/EBU Error Alarm Function
An “alarm” function monitors the received AES/EBU bitstream, indicating if there is a
parity error, abi-phase coding violation, areceiver PLL not locked condition or if the AES
transmitter set the validity bit. Upon detection of any of these errors, the 8218 continues to
look for subsequent error activity within the next 250msec. If the flag remains active within
that time frame, a+15V strobe is sent to the 8218 rear panel Remote Connector pin 10, and
the front panel “digital” LED flashes at a4per second rate (to differentiate this from the 2
per second rate indicating aloss of digital input, e.g. PLL not locked, forcing the unit to
switch to use the analog input). The +15V strobe and flashing LED remain for 4seconds
following the last detection of an error condition, after which pin 10 goes back to its normal
-15V state, and the “digital” LED reverts to its previous state. The ±15V strobe is capable
of delivering 10mA.
Remote Control Interface
The Remote Control Interface is aset of seven optically-isolated inputs and two outputs on
aDB-25 connector that can be activated by 5-12VDC or AC 50/60Hz signals.
The seven inputs allow you to select between various functions of the 8218:
•Analog/Digital Input.
•Pre-Emphasis On/Off.
•Operation Mode (Stereo, Mono From Left, or Mono From Right).
The two outputs on the Remote Control Interface are aDigital Pilot Reference Output Clock
and the AES/EBU error alarm function.
Location of 8218
Optimal Control of Peak Modulation Levels
The audio processing circuitry in most modem audio processors produces asignal that is
pre-emphasized to either the 50gs or 75gs standard curve, is precisely and absolutely high
frequency-controlled and peak-controlled to prevent over-modulation, and is filtered at
15kHz to prevent distortion caused by aliasing-related non-linear crosstalk in FM stereo
systems.

8218 Digital Stereo Encoder INTRODUCTION
If this signal is fed directly into the 8218, peak modulation levels on the air will be precisely
controlled. But if the audio processor’s signal is fed to the stereo encoder through any
circuitry with frequency response errors and/or non-constant group delay, the peaks will be
magnified. Peak modulation will increase, but average modulation will not. The average
modulation level must therefore be reduced to accommodate the larger peaks. Reduced
average modulation level will result in reduced loudness, and apoorer signal-to-noise ratio
at the receiver. To prevent this, the 8218 has abuilt-in, defeatable Overshoot Control Limiter
that can reduce overshoots of up to 9dB to less than 0.5dB. While this circuit introduces very
few (or no) audible artifacts for reasonable amounts of input overshoot (2-3dB with
relatively low duty cycle), nevertheless it is best to minimize the need for overshoot
compensation in the first place, so the amount of overshoot at the 8218’s input should be
minimized by the techniques described below. The Overshoot Control Limiter is not
designed to be used as an audio processor, and should not be used to apply more clipping to
an already processed signal. Use it only to remove STL-induced overshoot from aprocessed
signal.
Frequency response errors and non-constant group delay are typically introduced by
land/post-line equalizers, transformers, and digital links that use lossy data rate reduction
algorithms.
There are three criteria for preservation of peak levels through the audio system:
1) The system group delay must be essentially constant throughout the frequency range
containing significant energy (30-15,000Hz). If low-pass filters are present, this may
require the use of delay equalization. The deviation from linear phase must not exceed
±10° from 30-15,OOOHz.
2) The low-frequency -3dB point of the system must be placed at 0.1 5Hz or lower (this is
not amisprint!). This is necessary to ensure less than 1% overshoot in a50Hz square
wave and essentially constant group delay to 30Hz.
3) Any pre-emphasis used in the audio transmission system prior to the transmitter or stereo
encoder must be canceled by aprecisely complementary de-emphasis: Every pole and
zero in the pre-emphasis filter must be complemented by azero and pole of identical
complex frequency in the de-emphasis network (an all-pole de-emphasis network is not
appropriate).
Low-pass filters (including anti-aliasing filters in digital links), high-pass filters, transform-
ers, distribution amplifiers, and long transmission lines can all cause the above criteria to be
violated, and must be tested and qualified.
The 82 18can be located at the studio or transmitter, depending on the requirements of your
system. In the most common application, the 8218 will be located at the transmitter,
receiving left and right processed, pre-emphasized digitized audio via digital microwave, or
land/post-line and directly driving the FM Exciter/Transmitter.
If the 8218 is located at the studio, its composite output will be passed to atransmitter site
through acomposite microwave analog STL or through acomposite digital STL such as the
QEI “Cat-Link.”

INTRODUCTION Orban Model 8218
Transmission from Studio to Transmitter
There are four types of studio-to-transmitter links (STLs) in common use in FM stereo
service that can feed atransmitter-located 8218: digital STLs, video STLs with PC
adapters, analog land line (telephone/ line), and dual microwave.
All these links carry the left and right channels. These links are normally fed the pre-empha-
sized, peak-controlled left and right outputs of an appropriate FM stereo audio processor like
Orban’s OPTIMOD-FM 8200.
Digital links
There are several types of digital links presently available. They pass the audio in left and
right form, and may apply lossy data-rate-reduction processing to the signal to reduce the
number of bits per second required for transmission through the digital link. Such processing
will almost certainly distort peak levels, and use of such links will therefore require use of
the 8218 stereo encoder’s Overshoot Control Limiter to prevent over-deviation of the
transmitter. For example, ISO/MPEG Layer 2with dual-mono coding at 384kb/S typically
adds approximately 1dB of peak level. Lower rates rapidly increase the overshoot, with joint
stereo encoding at 192kb/S adding as much as 4dB overshoot. No station wishing to
maintain audio quality competitive with uncompressed STLs should use data rates of less
than 384kb/S.
Other links may use straightforward PCM (pulse-code modulation) without data rate
reduction. These can be completely transparent provided that they have AES/EBU digital
I/O. If these other links have only analog inputs and outputs, their input anti-aliasing filters
and output reconstruction filters must be rigorously designed to achieve constant group
delay over the frequency range that contains significant program energy. This is not
particularly difficult to do with modem over-sampled converter technology.
Older-technology converters with analog inputs and outputs usually exhibit rapid changes
in group delay around cut-off because their analog filters are ordinarily not group-delay
equalized. Additionally, they may exhibit quantization distortion unless they have been
correctly dithered. The installing engineer should be aware of all of these potential problems
when designing atransmission system.
Note that most modem audio processors (in particular, Orban’s 8200) have virtually no
power in their output spectrum above 16kHz. Therefore the input anti-alias filters in
older-technology converters can be bypassed; the audio processor protects against aliasing.
Note, however, that the link receiver’s output reconstruction filters cannot be bypassed;
these must have constant group delay.
NICAM is asort of hybrid between PCM and data-rate-reduced systems. It uses ablock-
companded floating-point representation of the signal with J.17 pre-emphasis. If equipped
with the optional advanced digital I/O card (8200D/SRC), the Orban 8200 can supply an
AES/EBU output that has been pre-emphasized to J.17. (The NICAM encoder must take
this PCM data stream and convert it to the NICAM representation.)
The 8218 has the ability to apply J.17 de-emphasis to its AES/EBU digital input, and can
thus accept the pre-emphasized output of aNICAM receiver, provided that the receiver has

8218 Digital Stereo Encoder INTRODUCTION
decoded the NICAM signal and converted it to PCM in AES/EBU form. (See Chapter 2for
acomplete discussion of the 8218s extensive pre-emphasis switching capabilities.)
Video microwave STLs with PCM adapter
The video STLs in use typically operate above 20GHz, with consumer PCM adapters (from
Sony or dbx, for example) to encode left and right audio into avideo-like signal. The quality
of signal received at the transmitter through this type of STL is high. However, the high
carrier frequencies make these links subject to rain fading. Other potential problems include
very sharp high-frequency cut-off, rapid changes in group delay around cut-off, and
quantization distortion. These problems can only be alleviated by use of digital I/O. To the
best of our knowledge, of these various units only the Sony PCM-601 has asuitable digital
I/O, which is SPDIF. (The 8218’s AES/EBU input will often lock to aSPDIF signal without
difficulty, although we cannot guarantee this for all cases.)
The Sony F-l -series units (including the above mentioned PCM-601) ordinarily operate at
asampling frequency of 44.056kHz. In our experience, most (but not all) of these units will
lock to a44. 1kHz signal. This will vary from one individual unit to the next. If you plan to
use aPCM-601 with an Orban 8200, you must use the 8200’s 8200D/SRC advanced digital
I/O card and set the 8200 to provide a44.1kHz digital output. You must then verify that the
particular pair of PCM-601s you are planning to use will lock reliably to 44.1kHz over
temperature.
The Sony and dbx encoders are no longer manufactured, but may be found on the used
market.
Analog land line (PTT/post office line)
Analog land line quality is extremely variable. Even the best land lines will have slight
frequency response irregularities and non-constant group delay, which will cause over-
shoots at their outputs. This will increase the peak-to-average ratio and will thus require use
of the 821 8’s Overshoot Control Limiter. In competitive environments these lines are never
suitable because of this overshoot, (see Optimal Control of Peak Modulation Levels on page
1-7).
Dual microwave STLs
Dual microwave STLs can provide satisfactory results if carefully designed. Otherwise they
can introduce non-constant group delay in the audio spectrum, distorting peak levels and
requiring use of the 8218’s Overshoot Control Limiter.
Some dual microwave links may be modified to meet the specification for frequency
response and phase linearity stated in Optimal Control of Peak Modulation Levels on page
1-7. Many such links have been designed to be easily configured at the factory for composite
operation, where the entire FM stereo baseband is passed, including the pilot tone and stereo
subchannel. The requirements for maintaining stereo separation in composite operation are
similar to the requirements for high waveform fidelity with low overshoot. Therefore, most
links have the potential for excellent waveform fidelity if they are configured for composite
operation (even if acomposite FM stereo signal is not actually being applied to the link).

Orban Model 8218
1-10 INTRODUCTION
If the STL microwave uses pre-emphasis, its input pre-emphasis network will probably
introduce overshoots that will increase peak modulation without any increases in average
modulation. We strongly recommend that you defeat the microwave STL’s transmitter
pre-emphasis and receiver de-emphasis. Perform pre-emphasis in the audio processing
system driving the link (like the Orban 8200). This reduces potential overshoot.
Line-Up Facilities
Left/Right Input Level
The Left/Right meter on the 8218 shows left/right input levels as a10-segment bar graph (5%
to 110%), absolute instantaneous peak-indicating. 100% is the threshold of the Overshoot
Control Limiter (when activated).
Composite Output Level
Composite modulation is indicated in percent modulation, absolute instantaneous peak
indicating. You ordinarily adjust the 8218’s output attenuators to make 100% on the meter
correspond to ±75kHz carrier deviation. Note that if subcarriers (SCAs) are applied to the
821 8’s subcarrier input, the meter will ordinarily read higher than 100%. For example, in
the U.S.A., if two subcarriers are used, the meter will usually read peaks of 110%,
corresponding to ±82.5kHz deviation.
The composite output meter indicates the sum of the encoded stereo baseband and the stereo
pilot tone. The composite meter may read lower than the Left/Right meters for three reasons.
First, if a100% audio peak does not coincide with the peak instantaneous value of the pilot
tone waveform, the composite meter will read below 100%. Nevertheless, it is accurately
showing the instantaneous peak modulation. Second, asmall effect called “pilot interleav-
ing” will reduce the composite modulation by 2.8% as the ratio of L-R to L+R increases
from zero to unity, even though the peak levels of the left and right audio have not changed.
Third, the sensitivity of the composite meter is reduced by 4% to accommodate operating
margin when the Overshoot Control Limiter is activated.
Pilot Injection Metering
You can switch the lower meter to read pilot injection in percent modulation. Most
government authorities require pilot injection to be between 8% and 10%. 9% is the value
customarily used.
About the 8218’s J.17 De-emphasis
When the Orban 8200 is set for “pre-emphasized” output (at 50(is or 75ps) the 8200D/SRC
digital I/O card in the Orban 8200 scales the gain of its optionally applied J.17 pre-emphasis
so that the J. 17 pre-emphasis gain at 15kHz is OdB.
When the 8200 is set for “flat” output (that is, the output of the audio processing receives
50(xs or 75(i.s de-emphasis before the audio is applied to the 8200D/SRC digital I/O card),
then the 8200D/SRC card scales the gain of its optionally-applied J.17 pre-emphasis so that

8218 Digital Stereo Encoder INTRODUCTION 1-11
the J.17 pre-emphasis gain at 15kHz is +6.9dB (when the audio processor is operating on a
50|_is pre-emphasis curve) or +8.85dB (when the audio processor is operating on a75|is
pre-emphasis curve.) The 8200D/SRC card adds this gain to make best use of the headroom
of the transmission channel it is driving.
These gains were determined by observing alarge amount of program material and adjusting
the gain so that the output level went as close to digital full-scale as possible without
exceeding it.
The 821 8’s J.17 de-emphasis operates in an exactly complementary way. When the 8218 is
set for pre-emphasis off (PRE-E OFF), it scales the gain of its J.17 de-emphasis so that the
J.17 de-emphasis gain at 15kHz is OdB. When the 8218 is set for PRE-E ON, it scales the
filter gain of its J.17 de-emphasis at 15kHz to -6.9dB (50jis pre-emphasis) or -8.85dB
(75|is pre-emphasis) The diagram below shows the situation for 75(is PRE-E ON.
J.17 de-emphasis <75us mode)
Figure 1-2: J.17 De-Emphasis Curve

Orban Model 8218
1-12 INTRODUCTION
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8218 Digital Stereo Encoder
Section 2
Installation
Installation of 8218
Figure 2-1 :Composite Output Impedance Jumpers
Figure 2-1 :Composite Output Impedance Jumpers
Figure 2-2: AC Line Cord Wire Standard
Figure 2-3: Wiring the 25-pin Optically-isolated
System Setup
CAUTION
The installation and servicing instructions in this manual are for
use by qualified personnel only. To avoid electric shock, do not
perform any servicing other than that contained in the Operating
Instructions unless you are qualified to do so. Refer all servicing
to qualified service personnel.