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NRSC Updates FM IBOC Measurement

Modulation Error Ratio method is now part of RF mask compliance guidelines

NRSC Chairman Milford Smith explains the committee’s latest actions. NRSC is sponsored jointly by the National Association of Broadcasters and the Consumer Electronics Association. Photo by Jim Peck
LAS VEGAS — The National Radio Systems Committee voted to add an FM quality measurement technique to its RF mask compliance guidelines for IBOC when it met concurrent with the NAB Show.

Also, members of the technical standards-setting body are working on RBDS several projects.

The measurement guideline update, a new standardized method for determining the transmission quality of an FM IBOC signal — Modulation Error Ratio — has been in the works for some time, and the guidelines will continue to be updated as IBOC technology progresses, said NRSC Chairman Milford Smith, vice president of radio engineering for Greater Media.

The general concept is that MER measurement can help a station measure the errors present in the data. MER tends to give the engineer a more useful view of system problems than the view obtained from bit error ratio measurements, according to the document “NRSC-G201-A, NRSC-5 RF Mask Compliance: Measurement Methods and Practice.”

The guidelines provide suggestions for how to analyze FM IBOC transmission, including what settings to use on different test equipment to make sure stations are all measuring the performance of their IBOC systems in the same way. This is important, given the variety of transmission facility configurations that are suitable for IBOC signal generation.

RBDS Subcommittee Chairman Barry Thomas added, “This is a document you can hand someone and say, ‘Here’s what you do. Go out and test these stations.'”

The IBOC Standards Development Working Group of the Digital Radio Subcommittee, chaired by Dom Bordonaro, chief engineer of the Connecticut cluster for Cox Broadcasting, worked on the update. Geoff Mendenhall, vice president of transmission research and technology at Harris, led the sub-group responsible for the updated portions with contributions from David Maxson of Broadcast Signal Labs and others.

Smith said the group will turn its attention next to a similar AM measurement.

The guidelines are available on the NRSC website:

Meanwhile, the RBDS Subcommittee is working on implementation guidelines to make station procedures simple and the data user experience more consistent.

Right now, receiver manufacturers implement the RBDS display in several ways. “We’re trying to reach out to broadcasters to let us know how they’re using it,” said Thomas. “Once you see what everybody’s doing, then it’s easier to develop a guideline.”

The hope is receiver manufacturers would see how stations are using RBDS as well as how they prefer to use it, so manufacturers will standardize the displays, which, in turn, would lead to more consistent consumer use.