You are likely familiar with the incredible FM signal analysis tools now available. One limitation of many of the most powerful tools is simply size. Being responsible for multiple markets, I find it difficult to justify big hardware just for spot checks. Fortunately we have some fixed tools available, but sometimes quick, portable measurements are needed.
The is a USB-powered FM scanning receiver, modulation and RDS analyzer that literally fits in a shirt pocket. It is only slightly thicker than my 250GB USB backup hard drive. The unit has a few connections: USB (data and power), an F connector for a supplied telescoping or external antenna, a BNC for FM baseband measurements, and a ⅛” stereo headphone jack for listening or connection to a PC.
Performance at a glance
75Ω F connector antenna input
87-108MHz in 100kHz or 200kHz steps
Decodes RDS and RBDS standards
3.5mm headphone jack
Composite MPX/RDS BNC input
How it works
The device uses PC software to control and operate the system. The tuning controls operate like a consumer radio, with programmable presets for up to five stations, an input selector for the baseband input and Windows buttons for the analyzer functions. The tuner station search settings can be adjusted between four RF levels, the step can be switched between 100 and 200kHz. There is an on-board 6dB attenuator and the demodulator has selectable de-emphasis (50µs/75µs).
It's apparent this device is targeted at RDS data analysis. The initial screen devotes a great deal to RDS (Figure 1). There is also a selector for the data mode: RDS or U.S.-Style RBDS. The display shows the RDS PS, PTY, call letters, radio text A and B, as well as the date/time. The RDS raw data is displayed as well. Very few U.S. radio stations use the AF list (alternative frequencies), but the initial display shows the presence of the list and its contents.
Figure 1. The initial screen displays a great deal of RDS information.
A particularly valuable data tool on the first screen is the Group Detector. This part of the display approximates an LED display that illuminates when the Band Scanner Pro detects one of the RDS groups. This is a useful thumbnail to see that certain RDS data is being transmitted with appropriate frequency. The Windows button Group Analyzer takes the next step showing measured percentages and group data flow for more in-depth analysis. There are tabs at the top of the display for each of the RDS Groups. Using those tabs, individual RDS groups can be observed. For setup, the RDS error level and BER display can be very helpful to find the best measurement location and are a good indicators of signal quality as well as for data measurement.
The Band Scanner Pro has a number of very familiar analysis tools. The Band Analyzer (Figure 2) is a scan of the FM band. There are two ways to do this: Scan, which shows relative signal strengths and Analyze, which augments the relative level display with frequency and the RDS PI code. After a band analysis is done, double-clicking on one of the station information boxes will tune the Band Scanner Pro to that channel. The reference level and marker can be moved with the mouse to help isolate parts of the band for investigation. The display can be zoomed, printed and saved, as a JPG, WMF, EMF or BMP. Clicking on Band Info will present the band analysis in table form including additional information for each station. This information can also be printed. It would have been helpful to be able to directly save this data as an Excel or CSV file but this can be easily rectified by making sure the Windows computer has a text-version print-to-file printer setup.
Figure 2. The Band Analyzer scans the FM band and shows a spectrum display.
The main and Band Analyzer screens have a Windows button for the FM Analyzer. This is a set of FM Modulation analyzer tools. The analyzer consists of a number of tabbed screens each with the familiar tuner display at the bottom. The main Modulation analyzer screen includes bar graph meters for total mod (MPX), RDS, Pilot, left/right audio and RF level. Each bar graph shows numeric values for the instant, minimum and maximum levels measured. More specific modulation analysis information is available using the display tabs:
FM Graph is a real-time graphical display of modulation parameters. The displayed time span can be varied between 1 minute and 10 minutes. Although it's possible to print, this is another place where a direct-export of a graphic file would be handy although print screen will suffice.
MPX Deviation, Pilot Level and RDS Level are similar graphical displays of the parameters over time. The display takes a little getting used to but it's a bold way of displaying the measurements in such a way to quickly see that the measurement is either within or out of tolerance.
The Left Right graph is a more conventional display of level over time.
The modulation analyzer screen shows various signal parameters.
The Band Scanner Pro has logging capability although its primary capability is to log RDS/RBDS data and not modulation parameters. This is an unfortunate oversight, particularly considering its remote capabilities.
For me, the attraction of this device was that it was a quick FM measurement tool I could fit in my laptop bag. It was something I could use to make a cursory measurement before I committed the serious hardware to the job. It will fit that bill very well but I found a nice little feature: Remote Mode. This mode turns a computer into a monitoring device over IP. By running this function and connecting the headphone jack to the computer audio input, a quick remote measuring device complete with a streaming server is created. The Band Scanner Pro software will stream encoded audio ADPCM, MPEG Layer 3, CCIT, Windows Media, GSM, and PCM at a variety of modes and bit rates. Remote Mode has its own Web interface that closely approximates the local Band Scanner Pro interface. This could be useful for quick remote listening applications that do not require the complexity or features of larger devices.
The help file was useful but I didn't find I needed to use it often. I initially had a minor problem with the display because I was using an odd resolution setting for my dual-monitor computer. The software needs 96dpi settings. Not a big deal. I'm not sure why I set it at 120dpi anyway.
Deva is currently testing a Band Scanner Pro with an on-board 12-channel GPS receiver. The new version will monitor up to 50 radio stations and plot the results on Google Earth. I look forward to an HD Radio version as well someday.
Thomas is VP of engineering for Lincoln Financial Media, Atlanta
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