IBOC Digital (HD Radio^TM) ERP Study

Feature avaialble for REC Clients with a $350 minimum spend.

Introduction

LPFM stations are authorized to operate In Band On Channel (IBOC) hybrid digital audio broadcasting. This is commonly referred to under the brand name HD Radio. HD Radio allows stations to have digital sound, enhanced station data and multiple audio streams.

To access this report, click on the Station Information option and then click on the Check for potential digital ERP link.

Maximum digital ERP allowed

Broadcast stations, including LPFM stations are authorized to operate HD Radio at 14 dB below carrier (dBc). This equates to a digital effective radiated power (ERP) of 4% of the analog ERP.

Stations can operate a digital ERP of up to 10 dBc, which equates to 10% of the analog ERP. In order to operate at a higher ERP, a contour study will need to be done to assure that there is no overlap between the LPFM station and any broadcast facility (including translators and boosters) on the first-adjacent channels.

First-adjacent channel protections for higher digital ERP

In MM Docket, 99-325, the FCC set out the following standards to use to determine at which digital power level a station can operate at:

Interfering F(50,10) contour of the LPFM station that reaches the 60 dBu contour of a first-adjacent channel station	Decibels below carrier (dBc) a station is permitted to operate at	Percentage of analog power	Digital power for maximum class (100W) LPFM station
51.2 dBu or above	14 dBc	4%	4 W
50.7 dBu~51.1 dBu	13 dBc	5%	5 W
50.3 dBu~50.6 dBu	12 dBc	6%	6 W
49.6 dBu~50.2 dBu	11 dBc	8%	8 W
Less than 49.6 dBu	10 dBc	10%	10 W

Reading the study

The myLPFM IBOC ERP Study identifies the facilities that are first-adjacent channel to your LPFM station and then performs contour studies per the FCC policies set forth in MM Docket 99-325 to assure that protections are provided to other FM facilities at the higher digital ERP.

For each other station, it will show each first-adjacent station, the ERP that was considered, whether there was overlap at each station and what the digital ERP would be reduced to as a result of that facility.

NOTE: Class B and B1 stations are measured to their 60 dBu service contours, regardless of channel.

FM broadcast stations operating at ERPs that exceed the maximum allowed for the service class at the height above average terrain (HAAT) that they are at will be adjusted to what the class maximum ERP would be from that location. This will be the most pronounced in grandfathered 'super power' stations. myLPFM takes the super power stations into consideration and will adjust the station's ERP to the class maximum. The system will make a note on the result when such an adjustment is made.

Asymmetrical HD operation

When a contour study shows that a reduction in digital ERP from 10 dBc is necessary due to a first-adjacent station on one of the two channels, asymmetrical operation allows a station to run the reduced carrier level on one sideband (where the overlapping station is) and a higher level on the other sideband. The use of asymmetrical operation has not been fully authorized by the FCC, but they will entertain experimental STAs. We hope that there will be a day when such operation becomes the norm. We will provide information on asymmetrical power levels in this report.

HD Radio^TM is a registered trademark of iBiquity, part of Xperi, Inc.