The trusty radio has finally received an upgrade—to the world of high definition. HD Radio, which has been gathering steam for a few years, sounds better and offers more channels than traditional radio. It also sends properly equipped devices text data like a song’s title and artist name as well as traffic, weather and stock information. One HD Radio even lets you pause programming in mid-stream, so you don’t have to miss a song or NPR story just because you’re drying your hair. And future HD Radio devices will record programming like television DVRs do now.

The Sony (above) and Coby Electronics (below) devices use HD Radio technology to play more stations at better sound quality.

This week, I tested three HD Radio devices to see what all the hype was about: Best Buy’s Insignia $50 HD Radio Portable Player (http://bit.ly/75FcIc); Coby Electronics Corp.’s $100 Portable HD Radio System (http://bit.ly/6G6g4Q); and Sony’s $160 HD Radio with Dock for iPod + iPhone (http://bit.ly/8c0Bqf). I also talked with iBiquity Digital Corp., the company that developed HD Radio technology and licenses it to broadcasters and radio manufacturers, about how this works.

I found some worthwhile offerings in HD Radio, like commercial-free, sub-channels within existing stations and better sound quality. IBiquity claims that HD Radio makes FM stations sound like CD quality and AM stations sound like FM; to my ear, this seemed to be true.

Overall, I didn’t hear enough incredibly great content or sound quality to want to run out and replace my old radios. Washington, D.C., where I live, supposedly offers 41 HD Radio channels, but I couldn’t find as many as that. Over 2,000 primary HD Radio stations and some 1,100 sub-channels can be heard in all 50 states and Puerto Rico, but some areas won’t offer as many stations, according to iBiquity.

Tuning in each HD station takes longer, like the way changing channels on a digital TV takes an extra second. But in my tests, this process took five seconds or more per change of channel. This kind of delay is enough to try anyone’s patience.

It might help to explain the technology behind HD Radio. HD Radio makes it possible for local broadcasters to transmit content via digital signals on existing AM and FM frequencies. The digital signals are encrypted and eliminate static heard in analog broadcasts, resulting in better sound quality. But they take longer to be decoded by HD Radio receivers.

Many people mistakenly think that in order to listen to HD Radio, they must pay an extra monthly fee like with satellite radio. If you buy an HD Radio device, you’ll only pay for it because the service itself is free; its price is built into the cost of the hardware.

Besides boosting the signal, HD Radio offers extra channels of programming you wouldn’t hear on a regular set. It allows existing FM channels to play additional content on “multicast” channels. Most multicast channels are commercial-free, and they appear on the radio’s display as HD2 and HD3.

Don’t confuse HD Radio with the text data that scrolls across the screens of many current radios, like my car radio. This is a non-audio service called Radio Broadcast Data System that has been around for a while.

Each of the radios I tested offered an HD Seek feature—a way of skimming through all stations to find and play those that could be heard in HD. But HD Seek didn’t stop on multicast channels; to get to those on each radio, I had to press buttons to tune up or down while listeningwhile already listening to to a main HD radio channel. Some HD Radio models have HD Seek tuning functions that find HD1 stations as well as HD2 and HD3 channels. I saved these HD2 and HD3 multicast channels in my radio presets so they were easier to find again.

While a radio was tuning in, or linking into, a channel (the process that took several seconds), an “HD” logo flashed on each radio’s display. This logo turned solid when the station was found and finally started playing. I listened to multicast channels like a bluegrass/country station from my local NPR channel. Another station’s two multicast channels played “South Asian” music and the Mormon Channel.

As its name suggests, Sony’s HD Radio with Dock for iPod + iPhone has a built-in dock for iPods, iPhones and iPod Touches. If, while using this radio, you hear a song on an HD channel that you like, you can hit a “Tag” button to save information about that song. The next time you dock an iPod, iPhone or iPod Touch into the Sony radio, these tags are transferred onto the portable player. When you plug that device into a computer and open the iTunes Store, a list of the tagged songs appears, making it easier to recall songs you liked and may want to buy. This radio is a tabletop model and has the largest display screen of the three radios I tested. It also comes with a remote. It saves up to 20 FM and 20 AM presets.

The Insignia HD Radio Portable Player is a much smaller unit that comes with earbuds and an armband for exercising. If this radio tuned in an HD channel that offered multicast sub-channels, these were indicated on the display with a “+” sign, like “HD1+.” The Insignia radio stores 10 preset stations.

The Coby Electronics Portable HD Radio System resembled a single, lightweight speaker with a wheel, six buttons and a digital display on it. IBiquity Digital said this model uses an older HD Radio technology that doesn’t offer as much reception sensitivity as the Sony and Insignia. Still, it was simple to use, and its wheel made it a cinch to tune in HD2 and HD3 channels. It stores up to 10 presets.

In September, when Microsoft’s Zune HD was released, I tested its built-in HD Radio, the only such device capable of pausing live radio content. I paused music and talk radio on the Zune’s HD Radio when my phone rang, then un-paused the station to resume. This doesn’t work if the device is turned off and on again before resuming play.

Along with stand-alone radios, HD Radio receivers also are becoming more common in home audio systems and in cars. But while HD Radio’s sound quality and extra channels are definite pluses, the number of available stations needs to improve to make the wait for the HD channels to start playing more tolerable.

Edited by Walter S. Mossberg.

Write to Katherine Boehret at mossbergsolution@wsj.com

Now, Disney (DIS) and CBS (CBS) already offer those same shows for viewing on the same day-after-original air date schedule on their own Web sites (though they aren’t presented commercial-free as they will be on Netflix). But that doesn’t seem to matter to Netflix (NFLX), which is clearly positioning itself as a one-stop shop for online delivery of movies and television shows.

And doing quite well at it, I might add. Wedbush Morgan Securities analyst Michael Pachter estimates that between 10 and 20 percent of Netflix’s 8.4 million subscribers use the company’s streaming service regularly.