65 Aleksandar Stamboliyski Str., 8000 Bourgas, Bulgaria
Tel: +359 56 820027, Fax: +359 56 836700
E-mail: [email protected] ,Web: www.devabroadcast.com
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INSTALLATION SPECIFICATIONS AND PRECAUTIONS
REGARDING THE RF ENVIRONMENT.
ANTENNA CONSIDERATION.
Attentively observing of the RF Environment, in which DB4005 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 DB4005 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 DB4005 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 DB4005 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 DB4005, 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 currently selected FM Band - 87.1-108 MHz (CCIR), 65-74 MHz (OIRT), 76-95 MHz (Japan).
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 DB4005 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.
