DEVA Broadcast DB7000 Operating and maintenance manual

MAINTENANCE AND OPERATION
INSTRUCTION MANUAL
Publish Date: 23-Oct-2014
DB7000
DSP-based FM Radio Re-Broadcast 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
RF Environment – precautions, installation specications and antenna types.............................14
De-emphasis and Pre-emphasis selection.....................................................................................14
Connecting – AC Power and Voltage Selection ............................................................................15
Panel Indicators, Switches and Connectors...................................................................................16
OLED Display ..............................................................................................................................16
Soft Buttons ..................................................................................................................................16
Navigational Buttons ....................................................................................................................16
Rear Panel.....................................................................................................................................17
Rear Panel Alarm Terminal ..........................................................................................................18
Operation..........................................................................................................................................19
Re-broadcasting limitations ..........................................................................................................19
Signal Strength .........................................................................................................................19
Multipath Distortion.................................................................................................................19
Co-channel Interface................................................................................................................20
First time power on .......................................................................................................................21
Front panel....................................................................................................................................22
Phones .....................................................................................................................................22
Loss...........................................................................................................................................22
Multipath ..................................................................................................................................23
Front Panel LCD Display, Navigational & Soft Buttons..............................................................24
Header Area .............................................................................................................................24
Soft Buttons...............................................................................................................................25
Main screen working area ........................................................................................................26
Re-broadcast Settings....................................................................................................................27
MPX out Conguration ............................................................................................................27
Stereo Generator ......................................................................................................................27
Injection levels ....................................................................................................................27
MPX limiter .........................................................................................................................28
Built-in RDS/RBDS Encoder ....................................................................................................29
Operating Modes and Pages ...........................................................................................................31
Home .............................................................................................................................................31
Band Scan page.............................................................................................................................32
Span control state: ...................................................................................................................34
Marker control state: ...............................................................................................................36
Parameter control state: ..........................................................................................................37
Bandscan page parameters ......................................................................................................37
Graphs page .................................................................................................................................38

Levels page ...................................................................................................................................39
RDS/RBDS Decoder Page.............................................................................................................43
Settings page .................................................................................................................................45
Settings Menu screen structure.................................................................................................46
Settings menu title ...............................................................................................................46
Navigation area ..................................................................................................................46
WEB Interface .................................................................................................................................51
Manual IP Address Identication..................................................................................................51
Network Discovery ........................................................................................................................52
Access............................................................................................................................................52
Main Screen...................................................................................................................................53
RDS/RBDS Screen.........................................................................................................................54
Bandscan Screen ...........................................................................................................................55
Status Screen .................................................................................................................................56
Log Screen.....................................................................................................................................57
General Settings Screen ................................................................................................................58
Tuner Settings Screen....................................................................................................................59
MPX Settings Screen .....................................................................................................................60
RDS/RBDS Settings Screen ...........................................................................................................61
Alarms Settings Screen..................................................................................................................62
Alarm notications ...................................................................................................................62
Alarm ........................................................................................................................................62
Communication Settings Screen....................................................................................................63
Network.....................................................................................................................................63
HTTP Server.............................................................................................................................63
FTP Server................................................................................................................................63
SNMP Agent .............................................................................................................................64
Syslog........................................................................................................................................64
GSM Modem.............................................................................................................................64
Application Server....................................................................................................................64
Audio Stream Server ................................................................................................................64
E-mail .......................................................................................................................................64
USB Port...................................................................................................................................64
Outputs Settings Screen.................................................................................................................65
Other Settings Screen ....................................................................................................................66
Firmware Update ....................................................................................................................66
Storage......................................................................................................................................66
System Log................................................................................................................................66
Factory Defaults ......................................................................................................................66
Reboot ......................................................................................................................................66

APPENDIX 1: Alarm Triggers .......................................................................................................67
Alarm Triggers ..............................................................................................................................67
Alarm Notication.........................................................................................................................69
APPENDIX 2: List of DB7000 settings..........................................................................................70
WARRANTY TERMS AND CONDITIONS................................................................................. 80
Product Registration Card..............................................................................................................81
APPENDIX A...................................................................................................................................82
RDS: Europe vs America ..............................................................................................................82
The RDS System ...........................................................................................................................82
APPENDIX C.1................................................................................................................................83
PTY Code Description Used in RBDS Mode – North America.....................................................83
APPENDIX C.2................................................................................................................................84
PTY Code Description Used in RDS Mode – Europe, Asia ..........................................................84

THIS PAGE
IS INTENTIONALLY
LEFT BLANK

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 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, DEVAenhances 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 DEVAproducts 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]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 7 -
General Information
DB7000 is a frequency-agile, digitally-tuned FM Re-Broadcast Receiver equipped with a
sophisticated and high-selective DSP based FM-tuner. The RF (IF) signal is digitalized as soon
as it enters the device and all signal processing is then made through DSP algorithms. The signal
being digitalized in this way, at the input, the equipment acquires measurement reproducibility
over time. The high-accuracy DSP based IF bandwidth lters help to solve difcult adjacent-
signal. The DB7000 measures conveniently all important parameters of FM transmissions. The
built-in monitoring system generates automatic warning messages in case of faulty or missing
data. The incredible processing power of the device enables all measurements to be refreshed
simultaneously and synchronously, thereby allowing for detailed readings of all the Multiplex FM
signal components.
The DB7000 has an easy to read, high-resolution OLED graphical display and ultra-bright
alarm indicators that allow reading the signal at a glance. An additional feature to the list of
DB7000 characteristics is that the RDS information contained in the processed MPX signal is
easily visualized and represented as RDS/RBDS Data and detailed RDS/RBDS Statistics. The
DB7000 is designed to support USB and LAN communication interfaces, allowing exibility in
remote connection and control of the unit. Easy channel status monitoring or audio listening from
everywhere is possible through your mobile phone. With the Audio Stream Server you can listen
to the audio of the received radio program.
The Band Analyzer function of the DB7000 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. In case of a transmission failure, maintenance staff will be immediately alerted via
E-mail,SNMP,orSMSwhich signalsthe technicianstorestoreanormal serviceas soonaspossible.
A high performance level and sustained reliability make the DB7000 to satisfy the requirements
of the most demanding broadcasters, as well as the satellite and cable operators. This product has
been designed with the latest state-of-the-art audio technology in use, and with very low harmonic
distortion!
Our DB7000 meets all necessary requirements of high level FM rebroadcasting.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 8 -
Product Features
• Sophisticated DSP based Digital FM Tuner
• Dual antenna ports with built-in RF attenuator
• Up to 100 dBµV direct RFAntenna Input
• Selectable wide range IF lter bandwidths
• FM Band 87.1 - 108.1 MHz Basic Spectrum Analyzer
• Advanced SNMP Ver.2C support
• Fully DSP-based management core
• Wide angle, easy to read OLED display
• Very Intuitive Navigational Menu
• Selectable De-emphasis - Off, 50µs and 75µs
• Built-in high performance Stereo Decoder
• Real Time Audio Program Streaming
• Remote Listening via optional GSM modem
• Easy to use WEB interface
• Apple and Android devices support
• SNTP for automatic sync 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
• 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, L & R Audio Levels
• Adjustable MIN/MAX alarms for MPX & RDS
• USB communication interface for local connectivity
• Headphone output with front panel level control
• Easy and intuitive Windows Application
• Firmware updates will ensure improved operation
• Accurate front-panel metering for local use
• Restore Factory Parameters option
• Wide operating voltage range: 100-240VAC
• 19” Professional Case for high RF immunity
• Easy Installation and Setup

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 9 -
TECHNICAL SPECIFICATIONS
RF INPUT
Tuning Range 87.1 to 108.1 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 Bandwidth 15 Increments (25kHz - 157kHz, Auto)
Frequency Response ±0.1 dB, 10 Hz to 86 kHz
Dynamic range 90 dB
STEREO DECODER
Frequency Response (L and R) ±0.1 dB, 10 Hz to 15 kHz
SNR (Stereo) 70 dB, 50 µs de-emphasis
THD 0.1%, 10 Hz to 15 kHz, 50 µs 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
ODA Yes
Group Analyzer Yes
BER Analyzer Yes
Group Sequence Display Yes
RDS RAW Data Display Yes
METERING ACCURACY
RF Level ±1 dB, 0 to 100 dBµV
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

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 10 -
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 3kg, 7lb

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 11 -
BLOCK DIAGRAM
Simplied block diagram of DB7000:
Because of the all-digital, minimalist-discrete-component nature of the device circuitry, we
have not provided schematic diagrams of the DB7000 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
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 12 -
Before you start
SAFETY PRECAUTIONS
• The servicing of electronic equipment should be performed only by qualied personnel;
• Before removing the covers DB7000 must be switched off and the mains cable unplugged;
• When the equipment is open, the power supply capacitors should be discharged using a
suitable resistor;
• Never touch the wires or the electrical circuits;
• Use insulated tools only;
• Never touch the metal semiconductor. They might carry high voltages;
• For removing and installing electronic components, follow the recommendations for
handling MOS components.
ATTENTION: DB7000 has an internal Lithium battery. Do not try to re-charge this battery!
Please contact us for detailed instructions in case the battery should be changed.

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 normal operation of DB7000, we recommend following the instructions listed below.
• Installtheunit inplaceswith goodairconditioning.DB7000is designedtooperate withinthe
ambient temperature range of 10 to 50°C. The equipment rack should be ventilated in order
for the device to keep its internal temperature below the maximum ambient temperatures;
• We do not recommend installation in rooms with high humidity, dusty places or other
aggressive conditions;
• Locate the device away from abnormally high RF elds;
• Use only checked power supply cables. We strongly recommend the usage of shielded
cables;
• Connect DB7000 only to reliable power supply sources. In case of unstable power supply,
please use Uninterruptible Power Supply (UPS);
• Use the device only with its top cover on to avoid electromagnetic anomalies. Otherwise,
this may cause problems with the normal functionality of the unit;
• For the normal remote operation of the unit, connect DB7000 to a good quality Internet
connection;
• For the normal operation of DB7000, check if the network settings past through all the
required data trafc.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 14 -
RF ENVIRONMENT – PRECAUTIONS,
INSTALLATION SPECIFICATIONS AND ANTENNA TYPES
The observation of the RF Environment, in which DB7000 is functioning, is necessary for
ensuring normal and reliable function of the device. In order for the device to work properly, the
best conditions according the standards listed below should be provided.
The usage of an external antenna is required because DB7000 is used for off air re-broadcasting
away from the transmitter site. Proper outdoor FM antenna, antenna location and direction should
be selected. The three most popular antenna types are: omni directional, unidirectional dipole and
directional multi-element array antenna.
Because of the low antenna gain, the bad signal to noise ratio (compared to any directional
antenna) and its high multipath interfaces reception, we do not recommend the usage of omni
directional antenna with DB7000.
The other type antennas: unidirectional dipole and directional multi-element array antenna are
much proper for your needs. We recommend the usage of factory made antenna or antenna system,
manufactured specially for the FM Radio Band 88 – 108 MHz.
The recommended working RF signal strength is in the range of 55-90 dBµV. If the input RF
level is above this range, we recommend using external RF attenuators with attenuation value
between 20 – 90dB.
After selecting the antenna type that will meet your needs, the next step is its installation. The
following important principles should be considered:
- Install the antenna far enough from walls, roofs, buildings or any transmitting equipment;
- The minimum spacing between the antenna and the closest object should be more than 3
meters.
One unit DB7000 re-broadcast receiver is used for re-broadcasting 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.
DE-EMPHASIS AND PRE-EMPHASIS SELECTION
As well known, there are three different de-emphasis selections. One of the problems with the
high quality VHF FM transmissions is that the increased audio bandwidth means that background
noise can often be perceived. It is particularly noticeable towards the treble end of the audio
spectrum, where it can be heard as a background hiss. To overcome this, it is possible to increase
the level of the treble frequencies at the transmitter. The frequencies are correspondingly attenuated
at the receiver in order to restore the balance. This also has the effect of reducing the treble
background hiss which is generated in the receiver. The process of increasing the treble signals
is called pre-emphasis, and reducing the treble signals in the receiver is called de-emphasis. The
rate of pre-emphasis and de-emphasis is expressed as a time constant. It is the time constant of the
capacitor-resistor network used to give the required level of change.
In UK, Europe and Australia the time constant is 50μs whereas in North America it is 75μs. The
de-emphasis and pre-emphasis should be selected depending on the region you are located or can
be disabled.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 15 -
CONNECTING – AC POWER AND VOLTAGE SELECTION
Before connecting theAC Power, make sure that the fuse rating is in accordance with the mains
supply at your location. DB7000 Power Supply Factory Settings are:
- 100-240 VAC;
- 1Amp Fuse.
CAUTION:
DB7000 will be damaged permanently if improper AC power supply voltage is applied. The
warranty DOES NOT cover damages caused by applying improper supply voltage or usage of
improper fuse.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 16 -
Panel Indicators, Switches and Connectors
OLED DISPLAY
DB7000 has easy to read, high-resolution OLED graphical display that visualizes all
measurements of the received signal and DB7000 settings.
SOFT BUTTONS
Used for navigation through the menus, quick access to the parameters, modes, functions and to
alter their values. The Soft Buttons indicators are placed on the bottom side of the OLED display.
Depending on the currently selected menu context the indicators change their function. The Soft
Buttons will be referred as (left-to-right) SB1, SB2, SB3 and SB4.
NAVIGATIONAL BUTTONS
UP–DOWN, LEFT–RIGHT and OK buttons, as the Soft Buttons, are used to navigate through
the menus selecting various functions and parameters of DB7000.

- 17 -
65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
REAR PANEL
1
2
3 45
6
7
8910
11 12 13
14
1. Mains connector, 110-240VAC, IEC-320 C14 type;
2. Fuse holder – 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 – Opto-isolated, Female D-Sub 15 pins.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 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

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 19 -
Operation
RE-BROADCASTING LIMITATIONS
Signal Strength
The signal strength is a major factor when a signal is re-broadcasted, measured and evaluated.
FM compared to AM is less susceptible to the inherent noise of the radio reception.
When speaking about FM broadcasting, it is the monaural reception which can tolerate and
prot from a much narrower IF bandwidth. The stereo reception adds all noise present in the 23 –
53 kHz sub-band. The amplitude component (AM) of the sub band is converted down to audible
noise and 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.
Better reception and measurement can be obtained by using highly directional outdoors antenna.
This will improve the signal strength and contribute in eliminating the multipath distortion.
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.
DB7000 has a multipath distortion detector and Front panel multipath LED indicator with
adjustable threshold. A bar graph indicator representing the multipath level of the received signal
can be reached under LEVELS menu.

65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: [phone], Fax: [phone]
E-mail: of[email protected] ,Web: www.devabroadcast.com
- 20 -
Co-channel Interface
In many populated areas, there is not enough space in the radio spectrum and stations might
be jam-packed. Poor frequency planning may also result in the mutual interface between the
broadcasting stations.
The inherent broad bandwidth of DB7000 re-broadcast 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.
We recommend you to observe the independent positive and negative deviation readings in
order to identify adjacent channel interference. If the positive deviation is higher than the negative
one, interference from a strong station above the monitored frequency would be indicated and
vice–versa. For 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.
Anyhow, the program deviation should be fairly symmetrical about the carrier frequency. Using
the built-inAttenuator can be of some help, but the usage of an outdoors directional antenna could
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.