Nautel Importer Plus - Synchronizing the SPS Sample Rate

Importer Plus Technical Instruction Manual Pre-installation tasks
Page 2-6 Issue 0.02 2010-03-29
Synchronizing the SPS sample rate
This section aids in assessing the feasibility of synchronizing the SPS sample rate to a 10 MHz
reference. This section includes the following topics:
• General considerations
• Methods to achieve synchronization
• Additional equipment
General considerations
You can achieve the best SPS audio performance if you synchronize the Importer Plus’ 44.1 kHz
audio sample rate to the master clock of the HD system. The difference in audio quality may not be
perceptible, or even important, given that SPS channels are typically lower quality audio. To
synchronize, you may require considerable equipment infrastructure (see “Using an HD-4 audio
card” on page 2-8) depending on the system configuration.
The station manager should review Methods to achieve synchronization in this section and determine
whether it is a worthwhile investment.
Methods to achieve synchronization
There are different ways to synchronize the SPS audio sample rate, based on the number of channels
and the location of the Importer. Consider the following:
Using a GPS synchronization unit for single channel applications. Nautel supplies either
an NAX240 GPS Synchronization Unit, or a built-in GPS synchronization card, with NE IBOC or
Exporter. Both of thee devices include a 44.1 kHz word clock output that can be used as the
synchronization source for an Importer Plus.
Using an audio processor as a sample rate converter. Some audio processors can provide
the sample rate conversion function. An audio processor must be able to accept either a word clock
or another AES input as a synchronizing signal for its output AES sample rate.
Importer location. If the Importer Plus will be co-located with the NE IBOC, Exporter or
Exporter Plus, and a suitable audio processor will be used to condition the SPS audio, the audio
processor may be able to perform the synchronization. See Figure 2.4 for a block diagram of this
setup.