OTHER TECH

HD RADIO IN THE REAL WORLD

Yamaha's RX-V4600 ($1,899) is the first digital surround receiver equipped with HD Radio, which is why I've had one at my side for a few weeks. Tuning is the same for stations with and without HD, so the first clue you've found an HD station is the appearance of its call letters on the display. Then the tiny HD indicator lights up and the sound blossoms, becoming quieter, clearer, and sometimes a bit more spacious. (The spaciousness probably comes from a cleaner transmission of stereo information compared with how it's done on FM.) On AM, the improved sound is due both to HD Radio's 18-kHz frequency response (analog response is limited to 5 kHz) and the addition of stereo (an AM station can't broadcast analog stereo and HD at the same time).

The station's call letters are followed by "HD1," the name of the main HD channel. If the station is multicasting, repeatedly pressing the Program Select button on the Yamaha's remote will bring up HD2, HD3, and so on. I discovered that at least one station in my area is experimenting with multicasting when I pressed Program Select a second time and it brought up "HD2" on the display with no accompanying sound. Simpler HD receivers and radios don't require this button - each multicast program simply shows up as another station on the dial.

In my New Jersey location, about 25 miles from New York City, I should theoretically be able to pick up as many as 23 FM and four AM stations transmitting HD. But nearly half the FM stations didn't reach me, and only one AM station did. Of the HD stations I could receive, I got a call-letter display from only five FM stations - WPLJ-FM (95.5), WNEW-FM (102.7), WKTU-FM (103.5), WAXQ-FM (104.3), and WLTW-FM (106.7). At home, I couldn't get a digital signal from WOR (710 kHz), the only nearby AM station with HD, but I've heard it in HD through a car stereo, and it definitely sounded like FM from the moment the digital decoding kicked in. My reception problems at home had more to do with my antenna than with the HD Radio technology or the Yamaha receiver.