HD Radio Time Alignment Drift Elimination, Resolved


Time-alignment issues continue to plague some FM radio stations with respect to their HD Radio air chain into the transmitter.

Now, these concerns may be greatly alleviated thanks to a new product release from Nautel and Telos Alliance.


Locking the FM and HD1 outputs from the audio processor through the remainder of the HD Radio air-chain into the transmitter is the key takeaway associated with the elimination of time-alignment drift.

And, as HD Radio uses separate but identical streams of audio on the analog and digital channels, these streams can arrive at the transmitter at slightly different times. “Diversity Delay,” which buffers the analog signal to blend its timing with the digital signal, is typically employed to ensure that there are no time shifts or artifacts in the signal heard by listeners when their receivers switch between analog and digital. However, minor errors in this time alignment can create audible artifacts. Excessive errors can cause content to be repeated or skipped entirely as the receiver blends from FM to HD1 and back.

There’s now a solution, as Nautel and Telos Alliance have locked the FM and HD1 signals in time so that the time alignment needs no correction, and the blending issues are eliminated.

“Our solution locks the FM and HD1 outputs at the audio processor, and keeps them locked as they pass through the remainder of the HD Radio air-chain right into the transmitter,” said Nautel CTO Philipp Schmid. “No extra boxes, additional audio codecs, radio receivers or correction methods are needed, and the Nautel/Telos Alliance solution utilizes ‘Made for Radio’ standards including MPX, µMPX, and E2X.”

A demonstration of what Nautel and Telos Alliance accomplished was demonstrated live during a recent webinar utilizing the Telos Alliance Omnia Enterprise 9s audio processing software, Gen4 Importer/Exporter, and Nautel technology, running on a Nautel HD MultiCast+. In the webinar, Nautel announced support on its HD MultiCast+ for the Telos Alliance Omnia Enterprise 9s.