Deva Broadcast from Bulgaria is an innovative company that has many tools for the broadcaster. One item, the model DB4004 FM monitoring receiver, is just one of its products marketed here in the United States.
This little gem, which takes up one rack unit of space, is a feature-packed tool for anyone monitoring single or multiple FM analog station clusters. Because it is DSP-based, the DB4004 can take monitoring of FM analog signals to a different level.
While mounted in a rack, the front panel provides access to a variety of settings and station presets, but it is not until you connect to its TCP/IP port that it shows its true strength. Once you are logged into the DB4004 Web server, it displays the main page where you have modulation meters showing everything from total modulation to multipath in real time. Here you will also have the ability to click through 20 station presets, switch between the dual antenna ports, or do a direct frequency entry. The two antenna ports give the monitor the ability to accurately monitor stations located in different physical directions. Automatic switching between them is a feature available when setting up the presets. Here you can select which antenna will be selected when calling up a particular frequency preset. If need be, a selectable attenuator can also be programmed.
A built-in spectrum analyzer can check the RF signal. If an oscilloscope display is more your style, the built-in oscilloscope can display everything from left and right audio, stereo Lissajous pattern to an RDS display. The spectrum analyzer and oscilloscope features can be accessed via the Web server for remote observations.
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The DB4004 comes with a logging function capable of scanning and logging a total of 50 preset frequencies and allows monitoring of left and right audio, pilot, RDS, RF level and more. The adjustable hold time of 10 seconds to 10 minutes on each preset tailors the logging interval. If set, the alarm functions can notify anyone of a potential problem with its configurable alarm settings. Notifications are sent via email, SMS, SNMP or GPO and can be customized with adjustments for alarm level thresholds and trigger/release times. This comes in handy to eliminate false alarms. When set up to scan and log the preset stations, the DB4004 generates a log file, which if need be, can be downloaded via its built-in FTP server for review at a later time.
| ||Performance at a glance || |
| ||■ LED bargraph for positive and negative deviation, left/right, L+R/L-R|
■ Level measurement with data history and 50-channel data logger
■ Built-in oscilloscope and spectrum analyzer
■ Built-in Web and FTP server
■ OLED display
Have you ever needed the ability to monitor the actual audio of a station from a remote location? If you are like me, there are times when it becomes a valuable tool to be able to listen to one of your stations when you are not in listening range. The DB4004 comes equipped with an audio stream encoder.
Access to the encoder is from the built-in Web server. The folks at Deva Broadcast have included the ability to adjust the quality of the stream as well anywhere from 64kb/s to 256kb/s.
This monitoring receiver includes a windows program that mimics most of the functions on the Web server. However, with the Windows program, the user is can place multiple DB4004s on a map and call them up by clicking on the map. This is convenient for those at the corporate level keeping an eye on things. A future release of the windows software will include a log manager section for downloading logs, managing logs in a database, and options to visualize the measurements versus time.
I did find one anomaly with the unit. For those wishing to monitor an analog transmission on a station that also transmits the HD Radio digital sidebands, the front panel modulation meter tends to read the analog modulation level 5-10 percent higher than what is actually being transmitted. This does not appear to affect its other monitoring capabilities.
Atkins is vice president/director of engineering of Backyard Broadcasting, Jacksonville, FL, and a member of the Society of Broadcast Engineers.