Field Report: Belar FMHD-1


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During the course of my career I've worked on many projects and dealt with lots of problems, many of which involved measuring a station's modulation or an injection level.

Belar FHMD-1

"What does the Belar say?" seems to be the phrase I most often thought or uttered during those occasions. Indeed, the company with the longest history in making modulation monitors for broadcast has got to be Belar Electronics. Its IBOC monitor is known as the FMHD-1, and it measures all the pertinent IBOC parameters, along with the standard analog items we're accustomed to. There's not enough room to address all its features, but I'll emphasize a few.

Let's start at the front panel. As you can see, the device is 2RU high, and the front panel includes a 640 x 240 pixel display and the rotary encoder wheel. There's also a headphone out. The rear panel is where all the important inputs and outputs are located.

Performance at a glance
Frequency agile
Off-air reception or high-level inputs
Meters analog and IBOC parameters
Simultaneous analog and digital outputs
Spectrum analysis
Bit error rate display
Four user-assignable alarm outputs
Ethernet or RS-232 control

There are eight analog output connectors, each of which can be assigned to any of the decoded audio streams including the analog modulation. Assignment of the outputs is done via the popup menu.

There are also three AES-3 outputs (75 ohms unbalanced) that can be assigned to any of the decoded (or demodulated) streams associated with the station to which the monitor is tuned.

Continuing along the top row, there are two separate analog composite outputs, along with two digital composite outputs that include SCLK, FS and SDATA.

Along the bottom row we have the RS-232 connector (male, so you may need a null-modem cable to connect to it); a DB-15 for access to four form-C relays that can be used to signal outboard equipment to alarm conditions that are user programmable; the Ethernet connector; and two sets of RF inputs. Note that you can use an antenna connection (if you use the monitor at a remote studio location) or you can use the dual high-level RF inputs if the FMHD-1 is installed at the transmitter site. You can combine the output from a separate digital transmitter with that from an analog transmitter right in the monitor device itself. You'll have to make sure the ratio of analog vs. IBOC is correct.

-- continued on page 2



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