Trends in Technology: Higher-power HD Radio


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Looking to add or upgrade IBOC? Here’s what you need to know.

ERI Lynx Series II

ERI Lynx Series II


Decisions

For many stations, making the jump to the -14dBc level (let alone the -10dBc level) is going to be like starting over again. Two major choices exist. Either you can decide to use your current main antenna for analog and IBOC, in which case you’ll choose a transmitter that is a combined amplifier, having the analog signal plus the IBOC signal in its output; or, you’ll opt to use your current analog transmitter, along with a smaller IBOC-only transmitter that feeds its own antenna. This antenna will have a power-gain that’s the same or close to your main antenna. This is a good option for those of us who have used a -10dB injector previously, because this size transmitter will likely have enough output capability to accomplish the -10dBc level (that is assuming the digital antenna’s power gain is the same as the analog antenna).

Shively 6813

Shively 6813


The major transmitter manufacturers that we know all have their own lines of IBOC-capable transmitters. Since the most basic requirement is being able to meet the TPO requirements, I’m including the latest information from these manufacturers – their published specs regarding their transmitter products (see below). As I wrote earlier, the other choice for increasing IBOC ERP is going with a different antenna. ERI has two different offerings. The first is called Lynx. This is a dual-input, dual-polarized antenna in which all elements are excited by both the analog and digital signals; power gain is the same for analog and digital. According to ERI it has the capability of achieving 40dB of isolation between the digital and analog inputs. The second is called Rototiller SA, which is a shared-aperture circularly-polarized antenna array. This type of antenna has the bays for the digital transmission interleaved within those of the analog antenna. The analog elements use opposite circularity than those of the digital antenna elements, providing the isolation needed. Shively Labs offers an interleaved antenna, their model 6813; Dielectric (SPX) also offers an interleaved antenna solution known as the HDR; and, Jampro offers the JSHD dual-input antenna.

As I wrote earlier, the other choice for increasing IBOC ERP is going with a different antenna. ERI has two different offerings. The first is called Lynx. This is a dual-input, dual-polarized antenna in which all elements are excited by both the analog and digital signals; power gain is the same for analog and digital. According to ERI it has the capability of achieving 40dB of isolation between the digital and analog inputs. The second is called Rototiller SA, which is a shared-aperture circularly-polarized antenna array. This type of antenna has the bays for the digital transmission interleaved within those of the analog antenna. The analog elements use opposite circularity than those of the digital antenna elements, providing the isolation needed. Shively Labs offers an interleaved antenna, their model 6813; Dielectric (SPX) also offers an interleaved antenna solution known as the HDR; and, Jampro offers the JSHD dual-input antenna.

I should note that each of the manufacturers listed here told me their dual-input antennas (or interleaved antennas) are ready to handle the -10dBc IBOC power level.

Now that the new power levels for IBOC transmission have become clear, it’s time for those of you who have been sitting on the fence with regard to IBOC to make the commitment to add it to your station.

Jampro JSHD

Jampro JSHD


It is much easier to put a digital transmission on-air now than it was five years ago; and even though many of our expectations haven’t been met (at least in terms of overall listenership), I continue to be a firm believer in the efficacy of this technology to provide a better experience for our listeners. We need to do everything we can to retain the ears that are giving us their attention.


Irwin is transmission systems supervisor for Clear Channel NYC and chief engineer of WKTU, New York. Contact him at doug@dougirwin.net.




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