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APT Codecs Deliver on the Internet
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GRAND RAPIDS, Minn. — We at Northern Community Radio operate two public broadcast FM stations in northern Minnesota, KAXE(FM) and KBXE(FM), each with full-power stations and a couple of translator sites. KBXE has just been constructed this year and I was seeking an STL for the station and interconnectivity to its sister station, KAXE.
When it came time for linking two studios and implementing a new STL I was faced with a number of choices on the market. Due to the fact that the two studios were some 70 miles apart a microwave link was not practical, so we needed an alternative economical way to have a 24/7 bidirectional stereo link with CD-quality audio. A dedicated MPLS (multi protocol label switching) metro Ethernet link between KAXE and KBXE was available but cost-prohibitive, so our only other option was sending the audio via IP over the open Internet.
LINKAGE
I also needed an audio codec that was solid and reliable but also a solution that could match the economical operational expenditure costs affordably with microwave links. But we also needed an STL solution from the KBXE studio to the KBXE transmitter site, which did not have high-speed Internet available at all.
 After evaluating available solutions from a number of vendors I decided to go with the Horizon NextGen from APT WorldCast Systems.
The SureStream technology using two Ethernet NICs and gateways creating redundant streams was unique. The feature set with the HNG including the relay closures and RS-232 data, which I needed to send control information, was strong. The front-panel audio level indicators were invaluable for quick status indication. APT WorldCast has a sound reputation for audio quality and IP transport. Lastly, the product was shipping. My need was immediate.
For the STL I had a single Internet provider, who provided me with bandwidth at each site. We installed two links per site to utilize the two Ethernet NICs on the Horizon NextGen. These links’ average speed is 4 Mbps upload and 7 Mbps download. Over each of the two links I send four tributary streams which are then recombined to create the broadcast-quality audio output, thanks to the APT SureStream technology running on the Horizon Next Gen.
The cost of these four consumer DSL accounts, two at KAXE and two at KBXE, with static IP address, is approx $60/month each. These accounts also serve as the office LAN Internet access, for uploading and downloading audio to Public Radio Exchange, and providing a gateway for our remote equipment. Since we operate KAXE and KBXE as a network where the same signal is carried on both transmitters, either studio can originate programming for the other’s broadcast chain. In addition, the paired HNG carry a satellite audio feed of our choosing along with contact closure data to synchronize profanity delays located at each studio. Separate profanity delays are used as the link between the studios is pre-delay, mix-minus audio to enable both studios to have hosts that can engage in bidirectional interviews and conversation between each studio with only 300 ms delay and all over public Internet.
The 17-mile STL microwave link using the other pair of Horizon NextGens we purchased has an upload download speed of 10 Mbps via a combination of license-exempt Ubiquity Nanobridge 2.4 GHz and licensed 11GHz Motorola PTP800 radios. This is more bandwidth than we need. SureStream, in fact, only requires a 700 kbps up/down link on each Ethernet NIC. We own this link and have zero monthly costs other than the power to run it.
Over the time we’ve been using the Horizon NextGens and SureStream technology we’ve been able to use economical consumer-level DSL and had a reliable signal with no dropouts. The Enhanced apt-X codec used is crisp and clean. There is a useful smart auto-reconnect feature and the ability to transmit contact closures and RS-232 data is very helpful.
The APT SureStream technology has made possible something that was conventionally assumed to be impossible: having a high quality, real-time audio link over the open Internet. After some initial tweaks and fantastic customer service from APT WorldCast, our units have been stable, providing a 24/7 studio-to-studio link connecting KAXE and KBXE with a bidirectional program audio that has pleased our staff and enabled connecting two studios with economical consumer level DSL service.
For information, contact Tony Peterle at APT WorldCast Systems in Florida at (305) 249-3110 or visit www.aptcodecs.com or www.surestream.ws
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