Barix Redundix Aid Vectis Radio

Dual stream technology greatly reduces audio glitches for island broadcaster
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NEWPORT, ISLE OF WIGHT, ENGLAND — Serving as “The island’s voice” for the Isle of Wight off the south coast of England, Vectis Radio delivers news, weather forecasts and community programming about the local economy and culture. Launched as an internet-only radio station in 2009, we went live with our first FM broadcast on 104.6 MHz in November 2017.

Barix Exstreamer, small box at lower right, and Redundix, upper left, at Vectis Radio transmitter site.

Barix Exstreamer, small box at lower right, and Redundix, upper left, at Vectis Radio transmitter site.

We faced a number of challenges in linking our studio to our 25 W transmitter, which is located basically in the middle of nowhere. The transmitter site is a rented space at a golf club at the top of a hill — a rather unusual place for a golf course, I’ll say! We could not use a direct microwave link, as the studio is almost at sea level, and part of the hill is in the way. Dedicated private circuits were cost-prohibitive, so we chose an internet-based approach.

We purchased Barix equipment for our STL encoder and decoder based on a recommendation from another community radio station. They were reasonably priced and straightforward to operate, so we deployed an Instreamer for our studio and an Exstreamer at the transmitter site. The encoder and decoder worked great right away, but I can’t say the same for the internet connectivity between them.

The internet service provider we use at the studio is reliable but could not provide a high-speed connection at the transmitter site, as it’s so far from any main communications highways. The local ISP near the transmission site put in a short microwave link to the transmitter, but like any such link, it is subject to issues like packet loss and rain fade. Those turned out to cause a lot of headaches for us.

Our on-air signal has suffered from sporadic, unpredictable audio glitches. Working with Barix support and Andrew Nordbruch, the managing director of local IT consultancy Wight Computers Ltd., we identified the cause of the glitches as significant, irregular packet loss on our internet link.

The packet loss varies considerably for no good reason. Weather does play a factor, as we get more packet loss when it’s very windy and rainy, but we’ll sometimes experience a great amount of loss even in clear conditions. The problem was so erratic that the ISPs were unable to resolve it for us.

Barix offered to let us test their new Redundix product, and we jumped at the opportunity. Redundix is designed to avoid such audible glitches by repairing lost RTP packets in the stream. It can do so using temporal redundancy on a single network link, and/or by sending a redundant stream over a second path.

With just one connection, we chose the former approach. A Redundix unit at the studio sends the 128 kbps MP3-encoded RTP stream from our Instreamer twice, once with a time delay; the second Redundix at our transmitter effectively merges the two into a single “healed” stream. Working together, Andrew and I determined the optimal time delay to be 800 ms. That introduces a bit of latency, but we can live with it to give us stable, high-quality delivery.

The Redundix units work well and clean up the transmission considerably. Our packet loss is severe enough that we still get glitches on occasion, but Redundix has eliminated at least 90 percent of them, and the glitches are significantly shorter as well — to the point that most listeners won’t even detect them. If we have the money in the future, we may add an ADSL link to the transmitter site as a backup and enable Redundix’s path-based redundancy as well, which I expect would eliminate the few tiny remaining glitches.

The Redundix interface provides a lot of valuable information about our network connectivity, and I love that I can access all of the Barix boxes — the Instreamer, Exstreamer and both Redundix units — through web-based interfaces. As the sole technical guy for the whole station, being able to troubleshoot any issues remotely from home is convenient. But the Redundix units themselves have helped us overcome our biggest issue, minimizing the impact of network packet loss and thus improving our audio quality for our listeners.

For information, contact Will Schmidt at Barix Technology at 1-866-815-0866 or visit www.barix.com.

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