IBOC basics

Figure 2. Combined transmitter configurations. Click to enlarge.

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Hybrid IBOC transmitters either combine the analog and IBOC signal at some level and apply them to the antenna (called a combined configuration shown in Figure 2) or the analog and digital transmitter signals are applied separately to an antenna (called a separate configuration shown in Figure 3). Whichever configuration you operate will determine the steps necessary to measure compliance with emission masks.

There are two emission masks that are important to check for compliance: The FCC emission mask and the NRSC emission mask.

Figure 3. Separate transmitter configurations. Click to enlarge.

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The FCC emission mask is defined in FCC Rule 73.317 and deals with the analog waveform. This article will focus on the NRSC emission mask. The NRSC emission mask definition and other important documents can be found at the NRSC website. NRSC-G201-A, An RF Mask Compliance Measurement Methods and Practice document was published in April 2010, providing guidance on how to demonstrate compliance. There are many ways to make compliance measurements and the benefit of the NRSC-G201-A document is that it simplifies the process, makes it easier to understand, and reduces the amount of time and measurement points for reliable compliance measurements.

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