International. Nautel and Telos Alliance announced a new approach to HD Radio time alignment, completely eliminating time alignment issues by blocking the audio processor's FM and HD1 outputs through the rest of the HD Radio air chain on the transmitter.
Because HD Radio uses separate but identical audio streams on analog and digital channels, these streams can reach the transmitter at slightly different times. Diversity delay, which buffers the analog signal to combine its synchronization with the digital one, is generally employed to ensure that there are no time changes or artifacts in the signal that listeners hear when their receivers switch between analog and digital. However, minor errors in this time alignment can create audible artifacts and excessive errors can cause content to repeat or skip altogether when the receiver is mixed from FM to HD1 and vice versa.
"Over the past decade, many vendors have designed complex solutions with built-in or complementary receivers that generate correction signals to try to minimize mixing problems," said Geoff Steadman, Omnia product manager at Telos Alliance. "Unfortunately, these solutions can affect the signal by hiding the underlying delay deviations. Unlike these other approaches, Nautel and Telos Alliance have now blocked FM and HD1 signals in time so that time alignment does not need correction and combination issues are completely eliminated."
"Our solution blocks the FM and HD1 outputs on the audio processor, and keeps them locked as they pass through the rest of the HD Radio air chain directly to the transmitter," said Philipp Schmid, CTO of Nautel. "No additional boxes, audio codecs, radio receivers or additional correction methods are needed, and the Nautel/Telos Alliance solution uses proven 'Made for Radio' standards, including MPX, μMPX and E2X. Our complete solution allows a station's HD Radio equipment to be location-independent, whether on the transmitter or in the studio, without the need for external time synchronization."
