WPR broadcasts in HD on many of its stations.  One of the most exciting aspects of this technology is the ability to deliver multiple channels of content on a single FM frequency.  Unfortunately there is a limited amount of digital bandwidth available for the additional channels.  About 96 kbps is available for audio or data.  Initially the only split available was 48 kbps for the main channel with the remaining 48 kbps available for additional channels.  Recent software verisons have allowed the main channel to drop to 32 kbps, thus allowing an even 32 kbps split for three channels of audio.  WPR has been broadcasting 48/48 for the main and a classical music channel but we wanted to look at adding our jazz channel as a 3rd HD service.  We needed to determine, however, whether or not the reduction in bitrate would significantly affect the audio quality.  I went to Casper to make some test recordings over the air.

My test setup in the hotel room…HD test receiver, audio interface for recording and laptop.

Making the recordings…I was able to get into the equipment remotely to control it for the tests but needed to be within range of this particular transmitter (Casper) in order to receive and record the audio.

Unfortunately the recordings from this test session were impaired but later repeating the tests revealed that there was NOT a significant degredation in quality.  We are clear to go ahead and add Jazz as a 3rd digital stream wherever possible!  Currently we have all three streams available on HD in Laramie/Cheyenne, Casper and Thermopolis.  Each site requires an “importer” to generate the additional streams.  More sites will come online as we purchase additional importers.