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Saturday, May 20, 2017

Desperately seeking digital

My radio hobby occasionally takes me out of the mainstream and into the esoteric. As an example, I chase HD broadcasts on AM, especially ones that aren't local and pose a challenge to pick up and decode. Essentially, it puts a new spin on the old hobby of AM radio dxing.

When (and if) you hear about HD radio, you probably first think of FM and the variety of programming on the secondary channels (HD2, HD3 and even HD4, where HD1 is the digital version of the main format.) Despite rumors of its demise, HD is still alive on the AM band, where the digital effect is really impressive. On AM, HD sounds like FM  mono - no static at all (apologies to Steely Dan), accomplished by buffering a slow data stream into full fidelity flawless audio.

HD on AM hasn't gotten much positive press in the 15 years it has been around - in fact, it has been maligned because of interference to adjacent channel stations, especially at night.  As a result, many stations that jumped on the bandwagon early are now turning HD off at night, or have dumped it altogether.

Generally, larger corporate-owned AM stations are still in the HD game, especially those owned by iHeart and CBS, which may have a financial stake in the success of digital radio, Smaller stations, the mom-and-pop shops that are struggling anyway, can't justify the expense of licensing fees, new transmitters and improved antenna systems for what amounts to minimal returns on the investment.

A complete list of AM stations licensed for HD can be found on this FCC page.

Unfortunately, conventional radios can't receive HD, but they are available on the retail market. Also, many high end new cars include HD as a standard feature, and portable and tabletop radios can be ordered online or found at electronic retailers like Best Buy and Crutchfield. Many of the available units are FM only, but a few also include AM, which generally plays second fiddle to FM in the analog world.

Listening during the day at home, I can decode broadcasts from Connecticut stations WTIC and WELI and New York powerhouses WCBS and WINS. Nighttime brings WBZ in Boston and occasionally others, like WHAM in Rochester, New York. One of these evenings, I hope to decode WGY at 810 kHz, where I pick up a blinking HD icon and strong signal, but no digital lock.

I was lucky enough to find a Sony XDR S10H tabletop receiver before it went out of production a few years ago. The unit has separate FM and AM antenna connectors, and the AM side is currently hooked up to my homemade AM rotatable loop.

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