The CBS Radio station recently installed one of ERI’s high level combiners (The 788 Series All Pass Diplexer) and increased the HD digital power at the station from -20 dBc to -14 dBc, quadrupling the signal strength. The FCC limit is -10 dBc, but there was no authorization needed for -14 dBc. The 788 can bring -10 dBc power, but the mid-Atlantic is crowded and it would interfere with 94.5 in Lancaster PA and Richmond, VA to the north and south. The power increase adds to effective digital coverage, but the real boost is in building penetration.
“This new combiner was the answer to what I was trying to do in the early two thousands as it is the Holy Grail for enabling high powered TPO stations to convert to IBOC,” an early IBOC/HD Radio innovator tells RBR-TVBR.
Bill Harland, ERI Vice President of Marketing adds, “The 788 Series combines analog and digital (HD Radio) with greater efficiency and better performance than other techniques currently in use. The All Pass Diplexer system does not have the high insertion loss of 10 dB hybrid injectors, which waste significant amounts of analog and digital transmitter power. The All Pass analog insertion loss is -0.35 dB or less and the digital loss is -1.4 dB or less. In addition, the group delay performance is superior to alternative high level combining methods and is readily correctable by currently available FM transmitters. Group delay of the analog signal is less than 350 nanoseconds and the digital delay is less than 600 nanoseconds. The All Pass Diplexer gives FM radio stations that are currently operating a -20 dBc IBOC power level with a 10 dB hybrid injector the opportunity to increase digital power without having to invest in a new transmitter.”
WIAD may be able to employ asymmetrical sidebands (94.5 or 94.9) that will possibly allow permission for one of those frequencies (likely 94.9) to be boosted to -10 dBc.
They first featured it the 788 at NAB last year. It won awards.
So far they have shipped the 788 to Hubbard St. Louis: WIL-FM and WXOS-FM; CBS Radio’s KMPS-FM Seattle and Clear Channel’s WSSL-FM Greenville/Spartanburg, South Carolina.
WIAD was flicked on at the end of January.