'Capable' or 'Ready' for Digital?
     

The First in a New Series of Hands-on Tips About HD Radio Implementation

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Photo by Cris Alexander. The IBOC interface board added to a Nautel ND Series transmitter.

As our company has gone through the process of converting its stations for HD Radio, we have learned a great deal. These early lessons were applied to later conversions, making the process much easier and more streamlined. By sharing this information with you, we hope to make your conversion process easier as well.

Over the next few months, I will, in this column, cover some of the practical considerations in HD Radio conversion for both AM and FM plants. I'll take things in more or less chronological order. In this, the first installment, I'll go over some of the AM conversion preliminaries.

Terminology

One of the biggest considerations in converting an AM station for IBOC is transmitter compatibility. A good percentage of modern solid-state transmitters are HD Radio-capable, but not necessarily HD Radio-ready.

To differentiate, an HD Radio-capable transmitter is one that can, with some reasonable amount of modification, be converted. An HD-ready transmitter is one that can directly accept the magnitude and phase signals from the digital generator and transmit an HD-R signal without modification.

If your transmitter isn't already HD-ready, the only way to know for sure if it is HD-capable is to contact the manufacturer and find out. It may well be that transmitters of a certain model number after a certain serial number are HD-capable, so be sure you have your transmitter's serial number handy when you make that call.

The answer you get from the manufacturer will tell you whether or not you will need to replace the transmitter or whether you can work with what you have. The manufacturer also can provide you with an accurate quote for the equipment needed to produce an HD Radio signal, including transmitter modifications, digital exciter and ancillary equipment.

If your transmitter cannot be converted for HD Radio operation and you will need a new HD Radio-ready unit, you have several choices, including Broadcast Electronics, Continental, Harris and Nautel. Others, such as Armstrong and QEI, have announced HD Radio-ready units or HD modifications for existing transmitters. Do your homework. Talk to engineers using these products in the IBOC hybrid mode.

Pricing will likely be similar, so performance, ease of installation and reliability become perhaps more significant in product selection. Also consider size, because you have to fit the new rig into available space or else enlarge/augment the space. Remember power requirements, cooling and other environmental factors.

The "guts" of the HD Radio generator essentially are the same for all manufacturers. At the core of each unit is a "digital up-converter" or "DUC" that is manufactured by Ibiquity Digital Corp.

The DUC is a Peripheral Component Interconnect (PCI) card that plugs into a slot in an industrial-grade computer motherboard. The HD Radio generator, then, is really nothing more than a computer built around the DUC. Differences between brands are minimal and largely cosmetic, in my view. Even the software is the same.

In our next column, I'll explain some of the preliminary antenna issues that AM stations must resolve before they can begin HD-R operation.

Got a suggestion for a future topic? E-mail crisa@crawfordbroadcasting.com.

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