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… How They Did It

... How They Did It

A stereophonic feed of Classical music from a CD player was uplinked through a standard 256 kb/s stereo PRSS channel, and received at the Satellite Transmission Center in Washington. A demodulated AES/EBU 48 kHz digital audio output was taken and fed into a Broadcast Electronics “Exporter,” which encoded the HD + PAD, and sent it out an Ethernet port at approximately 110 kb/s, as User Datagram Protocol.
The UDP data was then fed via Ethernet to the Radyne Comstream modem, uplinked up to the satellite again, and received at WUMB on its standard NPRSS downlink antenna. Another Radyne Comstream receiver/modem was used to reconstruct the UDP data, and it was fed into a Broadcast Electronics FXi-60 HD Radio/FM exciter with a new “Exgine” card.
The exciter fed a dummy load, and an off-the-shelf JVC in-dash HD Radio receiver was placed on the table near the Exciter.
Unlike TCP/IP, UDP/IP is designed for “one-way IP” data transmission. It does not have packet-reordering capability, and therefore has lower “overhead”, allowing higher payload throughput in a limited bandwidth channel. This characteristic makes UDP a good choice for digital audio transmission through a dedicated, one-way data channel, said participants.