DEVA Broadcast DB4004 User manual

MAINTENANCE AND OPERATION
INSTRUCTION MANUAL
Publish Date: 17-Aug-2015
DB4004
DSP-based FM Radio Monitoring Receiver
with TCP/IP Connectivity

Contents
Introduction........................................................................................................................................ 6
General Information.......................................................................................................................... 7
Product Features ................................................................................................................................ 8
Technical Specications .................................................................................................................. 9
Block Diagram .............................................................................................................................. 11
Before you start ................................................................................................................................ 12
Safety Precautions......................................................................................................................... 12
Operating Environment Recommendations................................................................................... 13
Installation Specications and Precautions regarding the RF Environment. Antenna Consider-
ation............................................................................................................................................... 14
Connecting AC Power and Voltage Selection ............................................................................... 15
Panel Indicators, Switches and Connectors................................................................................... 16
Front Panel – Left and Right Areas............................................................................................... 16
Left Area ................................................................................................................................... 16
Right Area................................................................................................................................. 16
OLED Display ..................................................................................................................... 16
Soft Buttons.......................................................................................................................... 16
Navigational Buttons ........................................................................................................... 16
Rear Panel..................................................................................................................................... 17
Rear Panel Alarm Terminal .......................................................................................................... 18
Operation.......................................................................................................................................... 19
A Word about Measurement Limitations ....................................................................................... 19
Signal Strength ......................................................................................................................... 19
Multipath Distortion................................................................................................................. 19
Co-channel Interference ........................................................................................................... 20
First Time POWER ON ................................................................................................................. 21
Front Panel – Readout Section (Left Side).................................................................................... 22
Phones ...................................................................................................................................... 22
Bargraphs and LED Indicators, Select Buttons ....................................................................... 22
FM MODULATING METERING ........................................................................................ 22
SELECT Button.................................................................................................................... 22
AUDIO DEMOD METERING............................................................................................. 22
L, R, L+R, L–R..................................................................................................................... 23
LOSS .................................................................................................................................... 23
Front Panel - LCD Display, Navigational & Soft Buttons (Right Side)........................................ 24
Display...................................................................................................................................... 24
Header Area.............................................................................................................................. 25
Soft Buttons............................................................................................................................... 26
Main Screen Working Area....................................................................................................... 27
Operating Modes and Pages......................................................................................................... 28
Home Page ............................................................................................................................... 28
“Preset” explained .............................................................................................................. 28
Creating a new Preset.......................................................................................................... 28
Bandscan Page ......................................................................................................................... 29
Span control state: ............................................................................................................... 31

Marker control state: ........................................................................................................... 33
Parameter control state: ...................................................................................................... 34
FFT Page.................................................................................................................................. 35
Scope Page ............................................................................................................................... 37
Measure Stereo page ................................................................................................................ 38
Graphs page ............................................................................................................................. 39
Levels page ............................................................................................................................... 41
RDS decoder page .................................................................................................................... 45
Settings page............................................................................................................................. 47
WEB Interface ................................................................................................................................. 53
Manual IP Address Identication.................................................................................................. 53
Network Discovery ........................................................................................................................ 54
Access............................................................................................................................................ 54
Main Screen................................................................................................................................... 55
RDS/RBDS Screen......................................................................................................................... 56
FM Graph Screen.......................................................................................................................... 57
MPX Screen................................................................................................................................... 58
Spectrum Screen ............................................................................................................................ 59
Scope Screen.................................................................................................................................. 60
Bandscan Screen ........................................................................................................................... 61
Status Screen ................................................................................................................................. 62
Log Screen..................................................................................................................................... 63
General Settings Screen ................................................................................................................ 64
Tuner Settings Screen .................................................................................................................... 65
Alarms Settings Screen.................................................................................................................. 66
Alarm notications ................................................................................................................... 66
Alarm ........................................................................................................................................ 66
Logger Settings Screen.................................................................................................................. 67
Logger Channel Settings ............................................................................................................... 68
Channel..................................................................................................................................... 68
Alarm Notication Type............................................................................................................ 68
Alarm ....................................................................................................................................... 68
Communication Settings Screen.................................................................................................... 69
Network..................................................................................................................................... 69
HTTP Server............................................................................................................................. 69
FTP Server................................................................................................................................ 69
SNMP Agent ............................................................................................................................. 70
Syslog........................................................................................................................................ 70
GSM Modem............................................................................................................................. 70
Application Server.................................................................................................................... 70
Audio Stream Server ................................................................................................................ 70
E-mail ....................................................................................................................................... 70
USB Port................................................................................................................................... 70
Outputs Settings Screen................................................................................................................. 71
Other Settings Screen .................................................................................................................... 72
Firmware Update .................................................................................................................... 72
Storage...................................................................................................................................... 72
System Log................................................................................................................................ 72

Factory Defaults ...................................................................................................................... 72
Reboot....................................................................................................................................... 72
APPENDIX 1: Alarm Triggers ....................................................................................................... 73
Alarm Triggers .............................................................................................................................. 73
Alarm Notications ....................................................................................................................... 75
APPENDIX 2: List of DB4004 settings .......................................................................................... 76
WARRANTY TERMS AND CONDITIONS................................................................................. 84
Product Registration Card.............................................................................................................. 85

THIS PAGE
IS INTENTIONALLY
LEFT BLANK

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
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- 6 -
Introduction
DEVA Broadcast Ltd. is an international communications and high-technology manufacturing
organization, its corporate headquarters and facility located in Burgas, Bulgaria. The company
serves the broadcast and corporate markets worldwide – from consumers and small businesses to
the largest global organizations. It is dedicated to the research, design, development and provision
of advanced products, systems and services. DEVA launched its own brand back in 1997 and has
nowadays evolved to become known as a market leader and internationally reputed manufacturer
of user-friendly, cost-effective and innovative broadcast products.
Creativity and innovation are deeply woven into DEVA corporate culture. Through successful
engineering, marketing and management our team of dedicated professionals creates future-
oriented solutions to improve customers’ performance. You may rely that all issues communicated
to our crew would be addressed accordingly. We pride ourselves on our pre and post-sales support
and purchase services, which along with the outstanding quality of our radio gear have won us due
respect and the market authority position.
DEVA best-of-breed solutions have become the best sellers for our partners. The strategic
partnerships which have been formed with industry leaders during all these years that we have been
operating on the broadcasting market, have proved us a reliable business partner and a valuable
asset, as our dealers worldwide would conrm. In constant pursuit of precision and long-term
satisfaction, DEVA enhances the reputation of our partners and clients alike. Furthermore, we have
already a proven merit as a credible partner provider.
Our portfolio offers complete line of high quality and competitive products for FM and Digital
Radio, Radio Networks, Telecommunication Operators and regulation authorities. For almost
two decades of intensive software and hardware development, we have achieved a unique price-
performance and endurance of our product lines. Our company’s multitude of equipment and
services is in line with the latest technologies and key trends. The most recognizable characteristics
attributed to DEVA products are their clear-cut, streamlined design, easiness of use and cost-
effectiveness: simplicity of forms but multiplicity of functions.
For us there is no stage when we deem that we have reached the most satisfactory level in our
work. Our engineers are in constant pursuit of new ideas and technologies to be captured in DEVA
solutions. Simultaneously, a strict control is being exercised at each step of any new development.
Experience and hard work are our fundament but the continuous improving process is what we
never leave aside. DEVA participates on a regular basis in all landmark broadcasting events, not
only to promote its products, but to exchange valuable know-how and experience. We are also
engaged in international large-scale projects involving radio and audio solutions which makes us
even more competitive on the global market.
All DEVA products are developed and produced in accordance with the latest ISO 9001 quality
control standards.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
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- 7 -
General Information
The DB4004 is our second generation digital FM Radio Modulation Analyzer. It combines our
long term experience in FM Radio Monitoring and FM radio measurement “know how.” The RF
(IF) signal is digitalized as soon as it enters the device and all signal processing is then made through
DSP algorithms. Digitizing the signal in this way, at the input, gives the equipment measurement
reproducibility over time. The powerful accuracy of the digital lters used in this equipment
enables the FM multiplex signals components to be accurately and repeatedly reproduced from
one device to another. The incredible processing power in the device enables all measurements
to be refreshed simultaneously and synchronously, thereby allowing for detailed readings of
all the Multiplex FM signal components. The DB4004 has easy to read, high-resolution OLED
graphical display and ultra-bright bargraph LED 60 segment indicators that allow reading the main
signal parameters at a glance. The built-in DB4004 Oscilloscope representing the observed signal
change over time enables you to visualize the most important signals participating in the process
of demodulating and stereo decoding. Complimenting the Oscilloscope mode, the Spectrum
analyzer mode allows spectral analysis of the input signal and part of DB4004 features. Spectral
components of the selected signal are determined on the basis of Fast Fourier Transform. MPX
Power and all other level measurements are supported by measurement history data. In addition
to the list of DB4004 features, RDS information contained in the processed MPX signal is easily
visualized and represented as RDS/RBDS Data and detailed RDS/RBDS Statistics.
Dependable off-air monitoring lets you keep an eye on other stations in the market as well as
measuring the important parameters of your own signal. Adjustable Alarms enable alerting for
most the important signal components and parameters to be generated and are fed to the Rear
Panel Alarm Terminal for remote alarm notication. The DB4004 is designed to support USB and
LAN communication interfaces, allowing exibility in remote connection and control of the unit.
The DB4004 is the most cost effective way for regular monitoring of the quality and continuity of
your station and up to 50 other FM Radio Stations, with many innovative features such as TCP/
IP connectivity, audio streaming, and automatic alerts for operation outside of predened ITU-R
ranges. In case of transmission failure, maintenance staff will be immediately alerted via E-mail,
SNMP, or SMS which allows technicians to restore a normal service as soon as possible. This
tool instantly enhances the quality control management for radio stations. The DB4004 allows
you to monitor all RDS/RBDS and other signal parameters from anywhere via its communication
channels TCP/IP, and allows GSM Connectivity via the optional external GSM Modem. Easy
channel status monitoring or audio listening from anywhere uses your mobile phone. With the
Audio Stream Server you can even listen to, skim, and record the audio from another station.
All the channel measurements and logs are saved in internal device memory. The built-in FTP
system manages the les by an assigned schedule. All the collected information is centralized in a
database and can be revised, played back, and sent automatically to the qualied staff as needed.
The Interactive Software-based Log Viewer tool allows the very detailed control and analysis
of any station from the list of monitored channels. The Band Analyzer function in the DB4004
presents an overview of all FM signals available, plus the RF signal strength of these stations.
Scans are possible within any section of the band in the FM band in 3 different modes. The
generated spectrum diagram shows the RF Level vs. the Frequency. Scheduled Band Scans can
also be enabled for RF intruder or pirate transmissions detection. The Deva Broadcast’s DB4004 is
a superb monitoring system designed as a powerful tool for FM Radio signal analysis and regular
off-air monitoring of your stations.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
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- 8 -
Product Features
• FM Band 87 - 108 MHz Basic Spectrum Analyzer
• Dual antenna ports with built-in RF attenuator
• Up to 100 dBµV direct RF Antenna Input
• Selectable wide range IF lter bandwidth
• Fully DSP-based core
• Bright, accurate bar graph LED metering of the Modulation and Pilot Levels
• Total and independent Positive and Negative deviation bar graph
• Left, Right, L+R, L-R bar graph LED audio level meters
• Wide angle, easy to read OLED display
• Very Intuitive Navigational Menu
• Built-in Oscilloscope for IF, MPX, Pilot, RDS, Left & Right display
• Levels measurement with data history
• Spectrum analyzer allowing checking of the RF Carrier and MPX
• Selectable De-emphasis - Off, 50µs and 75µs
• Quick Station access via 4 Presets
• Built-in Stereo Decoder
• Real Time Audio Program Streaming
• Remote Listening via optional GSM modem
• Built-in 50 channel Data logger
• Built-in WEB and FTP server
• Easy to use WEB interface
• Apple and Android devices support
• SNTP for automatic synchronization of the built-in clock
• RDS and RBDS decoder with BER meter
• Alarm dispatch via E-mail, SMS, SNMP and GPO
• Complete status reporting with SMS via optional GSM modem
• Protected access to the device settings
• Level Adjustable, Balanced Analog Audio Outputs on XLR Connectors
• Professional AES/EBU, SPDIF and Optical Digital audio outputs
• LAN port for full TCP/IP remote control and monitoring
• Adjustable MIN/MAX alarms for RF, Pilot Left & Right Audio Levels
• Adjustable MIN/MAX alarms for MPX, MPX Power & RDS
• USB communication interface for local connectivity
• Headphone output with front panel level control
• Firmware updates will ensure improved operation
• Accurate front-panel metering for local use
• Restore Factory Parameters option
• Easy Installation and Setup
• Wide operating voltage range: 100-240V AC
• 19” Professional Case for high RF immunity

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- 9 -
TECHNICAL SPECIFICATIONS
RF INPUT
Tuning Range 88 to 108 MHz, Frequency Agile
Tuning Step 10, 20, 50, 100 kHz
Tuner Sensitivity 30 dBµV
Antenna Ports Dual, 2 x BNC Connectors, 50Ω
Antenna Ports Isolation > 40 dB
Internal Attenuator 0, 10, 20 and 30 dB
Dynamic range 100 dB
FM DEMOD
IF Filter Bandwindth 15 Increments (27kHz - 157kHz, Auto)
Frequency Response ±0.1 dB, 10 Hz to 86 kHz
MPX Power ±12 dBr, 20 sec. integration
Dynamic range 90 dB
STEREO DECODER
Frequency Response (L and R) ±0.1 dB, 10 Hz to 15 kHz
SNR (Stereo) 60 dB, 50 µs de-emphasis
THD 0.15%@1kHz, 0.4% – 10Hz-15kHz, 50µs de-emphasis
Separation 50 dB, 50 Hz to 10 kHz, 50 µs de-emphasis
Crosstalk 52 dB
RDS DECODER
Standards European RDS CENELEC; United States RBDS NRSC
Error Correction & Counting Yes
AF Decoding Yes
CT (Time/Date) Yes
PI, PTY, DI, MS Yes
TA/TP Yes
RT (Radio Text), RT+ Yes
PS (Program Service name) Yes
TMC, ODA Yes
Group Analyzer Yes
BER Analyzer Yes
Group Sequence Display Yes
RDS RAW Data Display Yes

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- 10 -
FFT SPECTRUM ANALYSIS (RF, COMPOSITE, AUDIO)
Signal Sources RF (IF), MPX, Left, Right
FFT length 2048 points
Dynamic range 90 dB
SCOPE ANALYSIS (RF, COMPOSITE, AUDIO)
Signal Sources RF (IF), MPX, Pilot, RDS, Main, Sub, Left, Right
Record length 4096 points
Dynamic range 90 dB
METERING ACCURACY
RF Level ±1 dB, 0 to 100 dBµV
MPX Power ±0.2 dBr, -12 to 12 dBr, 0.1 dBr resolution
Total, Pos, Neg ±2 kHz, 10 to 100 kHz, 1 kHz resolution
Pilot, RDS ±0.5 kHz, 1 to 12 kHz, 0.2 kHz resolution
Audio ±1 dB, +10.0 to -55.0 dB, 0.1 dB resolution
OUTPUTS
Composite 3.5 Vp-p @ 75kHz, 75Ω, unbalanced BNC Connector
Audio (L, R) +12 dBm, 600Ω balanced XLR Connector
AES3 (L, R) 5.0 Vp-p, 110Ω , balanced XLR Connector
SPDIF (L, R) 3.0 Vp-p, 110Ω, unbalanced BNC Connector
Optical (L, R) Transmitter, TOSLINK
Alarms Programmable terminals on rear panel, optoisolated
Headphone 6,3mm (1/4”) Phone Jack
COMMUNICATION INTERFACES
USB B-type Connector
Ethernet 10/100 Base-T RJ45 Connector
GSM Modem 15 pin Male D-Sub Connector
MEASUREMENT STORAGE
Storage 2GB Build-in Memory Card
Data format Text, CSV
POWER
Supply 100-240V / 50-60 Hz / 25W
Connector IEC320
SIZE AND WEIGHT
Dimensions (W;H;D) 485 x 44 x 180 mm, 19” x 1.7” x 6.9”
Shipping Weight 540 x 115 x 300 mm / 2.7kg

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- 11 -
BLOCK DIAGRAM
A simplied block diagram of DB4004 is shown below
DSP
Analog
Tuner
Downconverting
FM demodulation
Stereo decoding
Metering
Control and
Communication
CPU
Ethernet
USB
User
controls
L / R
MPX
Rear Panel
Analog Audio
SPDIF
AES/EBU
Optical MPX Out
GPO
GSM Modem
Front panel
LED
OLED
Because of the all-digital, minimalist-discrete-component nature of device circuitry, we have
not provided schematic diagrams of the DB4004 in this Manual. Please, note that:
NO USER-SERVICEABLE COMPONENTS INSIDE.
REFER ALL SERVICING TO
QUALIFIED TECHNICAL PERSONNEL.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
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- 12 -
Before you start
SAFETY PRECAUTIONS
After removing any housing parts and electronic assemblies it is possible to get access to live
parts. It is essential to ensure that the subsequent safety rules are strictly observed:
• Servicing of electronic equipment must be performed by qualied personnel only.
• Before removing covers the equipment has to be switched off and the mains cable unplugged.
• When the equipment is open the power supply capacitors have to be discharged by the help
of a suitable resistor. During servicing unprotected and operating equipment:
- never touch bare wires or circuitry;
- use insulated tools only;
- never touch metal semiconductor cases because they may carry high voltages;
• For removing and installing electronic components, please follow the recommendations
concerning the handling of MOS components.
ATTENTION: DB4004 uses internal Lithium battery. Do not try to re-charge this battery!!! In
case you have to change the battery, please contact us for detailed instructions and more information
for the battery type.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 13 -
OPERATING ENVIRONMENT RECOMMENDATIONS
For the normal and reliable operation of the DB4004 device and reaching better measurements
we recommend to follow the next list of instructions:
• Please, install the unit only in places with good air conditioning. The unit has been designed
for operation within an ambient temperature range extending from 10 to 50°C. But because
adjacent, less efcient equipment may radiate substantial second-hand heat, be sure that the
equipment rack is adequately ventilated to keep its internal temperature below the specied
maximum ambient temperature.
• We do not recommend installation in rooms with high humidity, dusty places or other
aggressive conditions.
• Although it is expected that a DB4004 will be installed close to exciters (or transmitters of
even higher-power!), please practice reasonable care and common sense in locating the unit
away from abnormally high RF elds.
• Please, use only already checked power supply cables and sources. The shielded cables
usage is strongly recommended.
• We strongly recommend connecting the device only to reliable power supply sources. In
case of unstable power supply, please use UPS (Uninterruptible Power Supply).
• Please, use the device only with placed top cover to avoid any electromagnetic anomalies
which may cause problems of the normal functionality of the unit.
• Please, connect DB4004 only to good quality Internet connection. This is very important for
the normal remote operation of the unit.
• Please, check if your network settings pass through all the data trafc required for the
normal operation of the DB4004 unit.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
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- 14 -
INSTALLATION SPECIFICATIONS AND PRECAUTIONS
REGARDING THE RF ENVIRONMENT.
ANTENNA CONSIDERATION.
Attentively observing of the RF Environment, in which DB4004 is disposed and is functioning,
is necessary for ensuring of the normal and reliable working of the system. Best conditions in
accordance with the standards listed below must be provided for functioning of the system.
Depending on the application, the DB4004 monitoring receiver can be installed very close to
high power FM transmitters. Usually its antenna port is directly connected to any FM transmitter
monitor output or to directional coupler on the output of any combiner system. The typical RF
output level of such sources is too high for the normal operation of the DB4004 receiver. We
strongly recommend using external RF attenuators with attenuation value between 20 – 90dB for
reaching optimal RF output level in the 55-60 dBµV range.
Using external antenna is required when the DB4004 receiver is used for off air monitoring
too far from any transmitters or transmitter site. Very important step in such case is selecting the
proper outdoor FM antenna, antenna location and direction. The three most popular antenna types
are: omni directional, unidirectional dipole and directional multi-element array antenna.
The omni directional Antenna is not a good choice for using with DB4004, because of the low
antenna gain, the very bad signal to noise ratio (compared to any directional antenna) and its high
multipath interferences reception.
The other type antennas: unidirectional dipole and directional multi-element array antenna have
some directivity and antenna gain. These factors make these antennas much proper for your needs.
We recommend the usage of factory made antenna or antenna system, manufactured especially for
the FM Radio Band 88 – 108 MHz.
After selecting the antenna type that will meet your needs, the next step is the installation of the
antenna. You must follow several important principles:
- Install the antenna far enough from any walls, roofs, buildings or any transmitting equipment;
- The minimum spacing between the antenna and the closest object must be more than 3 meters.
One DB4004 monitoring receiver is usually used for the monitoring of one transmitter site,
transmitting more than one program. In such cases the best antenna that can be used is a directional
antenna directed exactly to this site.
If you would like to monitor more than one transmitter site, we recommend using antenna
system with separate antennas for each of the monitored directions.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
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- 15 -
CONNECTING AC POWER AND VOLTAGE SELECTION
Before connecting the AC Power, make certain that the internal Power Switch and the fuse
rating are in accordance with the mains supply at your location.
ATTENTION: DB4004 Power Supply Factory Settings are:
- 100 - 240 VAC
- 1 Amp Fuse
CAUTION: Permanent damage will result if improper AC supply voltage is applied to the
DB4004 device. Your warranty does not cover damages caused by applying improper supply
voltage, or use of an improper fuse.

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- 16 -
Panel Indicators, Switches and Connectors
FRONT PANEL – LEFT AND RIGHT AREAS
The DB4004 front panel can be provisionally divided into two main areas – Left Area and Right
Area. A brief description of controls and switches, indicators and displays located in both areas is
given below. For detailed information please refer to “Operation” on page 19.
Left Area
At the extreme left is located the Phones connector. Next to them are the sub areas of FM
MODULATION METERING and AUDIO DEMOD METERING with the appropriate SELECT
buttons and LED indicators. Both areas contain 60 segments LED bargraphs. The upper one is
used to indicate the Total Deviation, the Positive or Negative deviations divided each other and the
Pilot signal as well. The lower bargraphs are used to show the demodulated audio according to the
mode selected by the SELECT button on the left of them.
Right Area
OLED Display
– signals received by DB4004 can be viewed and analyzed by the built-in OLED display. This is
the display to visualize all the measurements of the received signal and show the various DB4004
settings.
Soft Buttons
– used to navigate through the menus, quickly access the parameters, modes and functions and
to alter their values. Their functions vary in accordance with the selected menu. On the bottom side
of the OLED display are located Soft Buttons indicators and they alter their meaning following
the function currently selected by the Soft Buttons. Pressing of a Soft Button, causes a visual
effect of pressing the appropriate button on the OLED Screen. Soft Buttons will be referred as SB1
(leftmost one), SB2, SB3 and SB4 (rightmost one) further in this manual.
Navigational Buttons
– UP and DOWN, LEFT and RIGHT and OK buttons are used for frequency selection and
similarly to the Soft Buttons to navigate through the menus selecting various functions and
parameters of the DB4004.

- 17 -
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REAR PANEL
1
2
3 45
6
7
8910
11 12 13
14
1. Mains connector, 110-240VAC, IEC-320 C14 type;
2. Fuseholder – 1A;
3. Audio Left Output - XLR;
4. Audio Right Output - XLR;
5. Audio AES/EBU Output - XLR;
6. Audio SPDIF Output - RCA;
7. Audio Optical Output - TOSLINK
8. MPX Output - BNC;
9. RF Input 1 (Antenna 1) - BNC;
10. RF Input 2 (Antenna 2) - BNC;
11. Ethernet T-BASE10/100 RJ45;
12. USB – type B;
13. GSM Modem – Male D-Sub 15 pins High Density;
14. GPO – Optoisolated, Female D-Sub 15 pins;

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- 18 -
REAR PANEL ALARM TERMINAL
12345678
9101112131415
1 - GPO1 Collector 9 - GPO1 Emitter
2 - GPO2 Collector 10 - GPO2 Emitter
3 - GPO3 Collector 11 - GPO3 Emitter
4 - GPO4 Collector 12 - GPO4 Emitter
5 - GPO5 Collector 13 - GPO5 Emitter
6 - GPO6 Collector 14 - GPO6 Emitter
7 - GPO7 Collector 15 - GPO7 Emitter
8 - GND
LOAD
1
9
GPO1
LOAD
1
9
GPO1

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- 19 -
Operation
A WORD ABOUT MEASUREMENT LIMITATIONS
Signal Strength
Signal strength is a major factor when a signal is measured and evaluated. FM as compared to
the AM is a much less susceptible to the inherent noise in radio reception.
On the other side speaking about FM broadcasting, it is the monaural reception which can
tolerate and prot from a much narrower IF bandwidth. Stereo reception adds all the noise present
in the 23 – 53 kHz sub-band. Moreover it is the amplitude component (AM) of this sub band
that is converted down to audible noise to be added to the program signal. That is why the noise
performance of FM-stereo can be as much as 20 dB worse than that of monaural broadcast.
As a general rule better reception and measurement can be obtained by using highly directional
outdoors antenna. Such antenna besides improving the signal strength, will contribute in eliminating
the multipath distortion.
A bargraph indicator used in DB4004 allows measuring the strength of the signal being received,
where the rule “the more the better” is in force. To reach this indicator, activate LEVELS menu.
Multipath Distortion
In FM reception, regardless of overall signal strength, a very important consideration is
that obstacles, (which an FM signal may encounter in the line-of-sight path) tend to reect and
disperse the signal in many directions. In many locations, especially in urban areas where many
tall buildings interfere with the direct transmitted signal or in suburban areas surrounded by hills
or mountains, an FM receiver may pick up a station’s primary signal but, also, several secondary
reections coming from various directions. These reections arrive at the receiver out-of-phase,
slightly delayed in time with the primary signal and tend to blur or distort the principal signal. The
degree of distortion depends on the number and relative strength of the reections.
The result, known as multipath distortion in FM reception can range from a low-level fuzziness
to a severely distorted sound quality, particularly at the high frequencies or treble. Multipath
distortion is especially troublesome in FM stereo reception.
DB4004 incorporates a multipath distortion detector and multipath bargraph indicator to show
the multipath level of received signal. The so mentioned multipath bargraph can be reached under
the LEVELS menu.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
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Co-channel Interference
In many populated areas, there just isn’t much room in the radio spectrum and stations will be
jam-packed in. Another thing which would result in mutual interference between the broadcasting
stations is poor frequency planning.
The inherent broad bandwidth of the DB4004 receiver is vulnerable from stations working on
the nearby frequencies, where signal strength will be the most important factor – the stronger the
interfering station, the stronger the interference effect.
One method to identify adjacent channel interference is to observe independent positive and
negative deviation readings. If the positive deviation is considerably higher then the negative
one, interference from a strong station above the monitored frequency would be indicated and
vice–versa. In this example the negative deviation can probably be trusted as an indication of total
carrier modulation, though this should be conrmed in free of interference RF environment.
In any event program deviation should be fairly symmetrical about the carrier frequency. Using
the built-in Attenuator can be of some help, but using of an outdoors directional antenna could
dramatically improve the situation with unwanted adjacent working stations. Other solutions
include a band-pass lter at the primary frequency or a trap at the interfering frequency.