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Trends in Technology: Monitoring HD Radio
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DaySequerra offers the M2.2R IBOC receiver/monitor. This 2RU device has both a high-level RF input and an antenna input. Some of its key features are:
Figure 7 shows the remote dashboard.
I've mentioned several times that it's (unfortunately) necessary to check the time alignment between the analog and digital streams for the MPS quite frequently. DaySequerra offers the M2DDM to solve this problem. This unit corrects time delay aberrations automatically in the background. There are several versions.
The single-station version includes internal digital delay. It is designed to be installed at a transmitter site. The multiple-station version sends real-time correction information via IP to embedded exporters. It is designed to be installed at a common receive location. The full remote-control version with the M2DDM dashboard can be accessed via IP. It also includes user-programmable, optically isolated alarm outputs that can correspond to loss of analog carrier, OFDM carriers and program silence, audio streaming available via IP, and it can send alarms outbound via email or text message.
Figure 8 is a block-diagram of the intended installation method at a transmitter site (single-station version).
More basic needs
The Inovonics INOmini 632 is an FM analog and HD Radio receiver for off-air broadcast monitoring capable of decoding up to HD8 multicasts. Analog and HD Radio digital programs are both accompanied by digitized text and housekeeping data including FM RDS, RT+ tagging data and IBOC PSD, which are shown on the front-panel LCD display.
When the 632 is set to receive IBOC it does not automatically revert to analog reception if the digital signal is lost. A jog wheel navigates the receiver's menu tree. Analog and AES audio provided with rear-panel tallies for carrier loss, digital program loss and analog audio loss.
Perhaps all you want is a monitor to pick up digital transmissions, sending the audio to all the normal places. In that case, consider the Sangean HDT-1X. Clearly it doesn't have all the bells and whistles of the monitors I've mentioned so far, but it does have the following useful features:
Obviously you could tack on your own widgets to the audio outputs of this device so that you can be made aware of loss of digital audio, at the very least.
Receiver and modulation monitor manufacturers have caught up to us now, and it's far easier to build an IBOC monitoring system than it was five years ago. Obviously all the new features available with the digital transmission scheme we're using necessitate even more complexity in the monitoring arrangements. The good news is that the new technology seen in the products I've discussed also have positive benefits for monitoring our legacy transmission methods as well.
Irwin is transmission systems supervisor for Clear Channel NYC and chief engineer of WKTU, New York. Contact him at firstname.lastname@example.org.
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