Moseley Provides Digital Links for Jamaica
     

The Moseley Starlink NXE1 installed at the Orcabessa transmitter site.
MIAMI — The challenge was to serve 95 percent of Jamaica with a superhigh-quality FM signal. This project was ambitious and never had been attempted in Jamaica, the land of analog composite STL links that were daisy-chained around the island. The objective was to build a large studio complex and nine transmitter sites on remote mountaintops all around the island nation. We wished to create a redundant STL system that would provide high-quality digital audio to each transmitter site. It would also give the studio the ability to confidence monitor off-air audio from each site and control each site via a remote control system.

OBSTACLES

Logistically there were many obstacles: tower location, availability of power, transmitter building facilities with controlled environments, distribution of audio, remote control of all facilities, and the ability to monitor and control these systems from the United States.

Working with the engineering team at Moseley, we first explored the idea of using multiple Moseley Starlink STLs with two independent loops around the country, one clockwise and the other counter clockwise. AES switches would select the appropriate loop at each site if there were failures.

As we progressed with our investigation, a different idea was developed. Moseley suggested a bidirectional redundant IP radio network based on the Starlink radios that would feed all sites simultaneously, giving each transmitter the identical audio feed. We needed a device to create two main audio streams to feed the sites and one return audio stream. The Moseley Rincon Digital Audio Transporter multicodec was a perfect fit for our needs.

The Rincon was capable of providing two high-quality uncompressed audio streams to feed all sites (the second was the backup audio stream) and the Rincon would easily provide a low bitrate stream back to the studios so that actual off-air signal monitoring was possible. Rincon streams could be individually configured for the appropriate protocols to keep bandwidth limitations from being exceeded. A big bonus was the available bandwidth for remote control systems and webcams for all sites.

Starlink NXE1 bidirectional radios were configured in a self-protecting ring network around the island connecting the transmitter sites. The Starlinks were equipped for bidirectional IP transport. The IP network was configured with two paths that were controlled by Cisco switches that used the Spanning Tree Protocol to direct packets appropriately. If one site went down, the system would automatically reconfigure itself and keep all remaining sites functional.

The Starlink “ring” connects the transmitter sites in Jamaica.

Rincons are the audio engines. Main and backup AES digital audio is sent from a Rincon at the studio onto the wireless IP network and delivered to all sites nearly simultaneously via the Starlink network. Each site also has its own Rincon which feeds audio from the Starlink to the transmitter at that site. Using the compression algorithms available in the Rincon, 64 kbps audio for confidence monitoring was sent back in the direction of the studio.

The Rincons were configured with the appropriate error correction to address the harsh radio environment and frequent spurious emissions in Jamaica. Because the STL system was set up as an IP network, Moseley was always able to remotely troubleshoot or configure any Rincon in the network from their California facility when help was needed during construction and would still be able to provide aid. Since we run dual UPS systems at each site, the redundant power supplies in the Rincons were each hooked to a different UPS system.

At this time FYAH105 is the only radio network facility in Jamaica with digitally-delivered identical AES audio feeding all transmitter sites and the ability to monitor and remote control all nine radio facilities. The majority of all engineering is done from the U.S. because the Moseley IP network allows us to “see” all transmitters, STL links, Rincons and other site equipment. It’s an amazing system and the reliability has been excellent.

For information, contact Bill Gould at Moseley in California at (805) 968-9621 or visit www.moseleysb.com.


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