NRSC-G201 RF Mask Compliance Measurement Guideline Adopted

Nearly two years of work came to fruition at the National Radio Systems Committee (NRSC) DRB Subcommittee meeting, held last Saturday, April 18, 2009 in Las Vegas, NV (in conjunction with the 2009 NAB Show, www.nabshow.com), when the Subcommittee adopted an important NRSC Guideline document dealing with measurement of RF mask compliance for AM and FM in-band/on-channel (IBOC) digital radio signals.

NRSC-G201, NRSC-5 RF Mask Compliance: Measurement Methods and Practice, was adopted by the Digital Radio Broadcasting (DRB) Subcommittee which is co-chaired by Andy Laird, Vice President and Chief Technology Officer, Journal Broadcast Group, and Mike Bergman, Vice President, New Digital Technologies, Kenwood USA. It was developed by the Subcommittee’s IBOC Standards Development Working Group (ISDWG) which is chaired by Dom Bordonaro, Chief Engineer, Cox Radio, Connecticut. The ISDWG is also the group responsible for development and subsequent modification of the NRSC-5 IBOC Digital Radio Broadcasting Standard.

The idea for developing this Guideline arose from the ISDWG’s work on developing the “B” version of the NRSC-5 IBOC Standard. The group recognized that, given the variety of IBOC transmission facility configurations as well as the need to characterize IBOC RF signals by both equipment manufacturers (during construction and testing of IBOC transmission equipment) and broadcasters, various methods must be utilized to determine compliance with the RF masks specified by NRSC-5. The purpose of the Guideline is to provide background information as well as detailed instructions on the best methods and practices for determining compliance, for both hybrid AM and hybrid FM IBOC, for the situations most likely to be encountered.

Some of the topics covered in this new NRSC Guideline, which is nearly 100 pages in length, include the following:

Modulating signals and compliance measurement (Section 4.2 – FM IBOC) – the signal(s) used for modulating the analog portion of the HD Radio hybrid FM IBOC signal can introduce variance in RF mask compliance measurement results. Since the shape of the PSD envelope of the analog portion of the hybrid signal is determined by the modulating signals applied to the analog carrier, a test signal is recommended which results in repeatable measurements, thereby eliminating variances due to the modulation. The recommended test signal has been found to be more “demanding” against the mask (by about 2 dB) than using “pink” noise or program audio.

This document will be available free-of-charge on the NRSC’s web site at www.nrscstandards.org, following a final, procedural review which will take approximately four weeks. Additional information about the NRSC, including information on becoming a member, is also available on the web site.