Washington - Jul 23, 2009 - To illustrate a simple and effective procedure for determining the allowable increase in IBOC power during an interim power increase period, NPR Labs has developed a set of procedures for Reserved Band and Non-Reserved Band stations, based on the FCC's standard allocation techniques.
While allowable power can be calculated using tools available on the FCC website for calculating distances, bearing and field strength, NPR Labs, with computer processing and assistance from Cavell Mertz and Associates, has performed the calculations for all licensed stations in the U.S. and made them accessible through the lookup tools on this page.
The NPR interim approach would allow any station to increase IBOC power subject to existing minimum protection requirements, according to individual station classes for both the proponent (IBOC) and potentially affected stations on first-adjacent channels. The adjacent channels contain the OFDM subcarriers of the proponent IBOC station, and are effectively co-channel to the first-adjacent neighbors' analog FM signal.
Because -20dBc (1 percent) IBOC power is currently authorized for all stations, and Section 73.207 of the FCC rules prescribes minimum first-adjacent separation distances for all class combinations, NPR proposes to increase the IBOC transmission power proportionately with increased distance, such that the F(50,10) interfering field strength is maintained at the protected service contour of the first-adjacent neighbor.
To access the tool, go to www.nprlabs.org/publications/distribution/interimIBOCpowerallowance/index2.php.