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Published March 15, 2008

 

Sangean HDT-1X HD AM/FM Tuner

If you listen to US radio at all, you may have heard something in the last year about HD Radio. It’s the first major advancement in broadcast technology since the advent of FM stereo in 1961, but there’s a lot of confusion about what it really is.

HD stands for hybrid digital (not high definition). In an HD broadcast, a digital signal is sent at the same frequency as the standard analog signal. Because the two signals exist in different domains -- analog and digital -- they can occupy the same airspace at the same time. (You can read more about this fascinating technology at www.hdradio.com/what_is_hd_digital_radio.php.)

In practical terms, HD Radio gives you less multipath interference when you’re listening to FM in the car. You get multipath when a signal is coming at you from at least two different directions, one of them directly from the broadcast tower and one reflected off a hill or building. The reflected signal arrives a split-second later than the direct signal -- the difference between the arrival times is just enough to cause interference, which is audible as an annoying spitting sound. But as long as you’re within range of a strong HD Radio signal, multipath is a thing of the past.

One of the biggest advantages of HD Radio is that it allows stations to broadcast multiple programming channels. For instance, the second digital signal of my local public classical station is my favorite: jazz 24/7. Our local classic rock station offers analog and digital streams of its regular programming, plus a second digital stream of deep-cut rock classics. Any number of HDR programming options are available for stations to plug in and play, from full-time grunge to Americana to blues to the BBC World Service. And once you’ve purchased an HDR tuner, it’s all free.

Most big-box electronics retailers stock only one or two HDR models. But the radios won’t be able to lock on to the HD signal, so you’ll have to take their word that HD is a good thing. So far, the Internet has proven to be the best place to buy HD radios for the car or the home (portables are coming in the next year).

Description

One of the most fully loaded HD Radio models now available is the subject of this review: the Sangean HDT-1X ($250 USD). Sangean has long built amateur radio equipment and multiband radios -- for many years, they made the shortwave radios sold by RadioShack -- and have a reputation for bulletproof construction.

The HDT-1X looks like a typical matte-black tuner of standard proportions: 16.9"W by 2.75"H by 10"D. Most of its front-panel controls are those you’d find on any analog tuner, and most are duplicated on its small but functional remote control. From left to right on the front panel are: a Power button (it glows red when the HDT-1X is in standby mode), then a 0-9 numerical keypad with two small pushbuttons. One of these lets you select among 20 FM and 20 AM presets; the other lets you enter a station’s frequency directly. In the center is a large, multifunction LCD display. Depending on the signal you’re tuned to, it can show that an HD signal is being received, display the station’s call letters as well as its frequency, provide Radio Data System (RDS) info such as the title and performer of the song being received (if the station broadcasts such data), or indicate normal (analog) reception. The display options offered via the Info button to the right of the screen include the time, incoming signal strength, station frequency, and the audio spectrum (divided into ten bands) of the signal being received.

Hold down the HDT-1X’s Info button for two seconds and you can cycle through several setup options. System Reset resets the tuner to its factory defaults. The display’s contrast can be adjusted from 0 to 9, and the strength of its backlighting can be set to Bright or Dim. (Choose Dim -- with Bright, you could light up Yankee Stadium in a heavy fog.) Through these advanced options, it’s also possible to force the tuner into Stereo Only or Mono Only mode; Analog Only or HD Only; or, for you broadcast engineers out there who want to sync your analog and digital signals, a unique Split mode provides the digital signal in the left channel and the analog signal in the right. These are pretty much set-and-forget, onetime operations, so it makes sense that Sangean has placed them in a subsidiary menu.

Next to the Info button is the all-important Band selector. Then come three rocker switches, which control various other tuning schemes. The first is a manual tuning control that travels the FM band in steps of 0.1MHz. The second, Seek, searches for stations up or down the dial until it’s released, at which point it stops at the next station. The last is HD Seek, which searches only for HD signals. HD reception is automatic if the station to which you’re listening is broadcasting an HD signal. The "HD>" symbol on the display will blink until the tuner has locked to the digital signal, at which point the audio output switches to the digital signal.

The rear panel is sparsely populated. From the left are: an F-connector for the FM antenna, two connectors for the supplied AM loop antenna, two RCA audio output jacks, an S/PDIF optical digital jack, and a polarized AC jack.

Performance

Were this a typical tuner review, here’s where I’d cite the techy stuff -- sensitivity, selectivity, capture ratio, etc. However, Sangean provides virtually none of the usual tuner specifications. So on a single day (weather conditions affect FM reception), to get some baseline analog data, I conducted a face-off between the Sangean HDT-1X and my Magnum Dynalab Etude tuner, using the same antenna for both. This turned out to be a good test of the Sangean’s basic performance.

The Sangean’s analog reception can only be called superb. There are 47 local FM signals that I should be able to receive, all broadcasting from the Cincinnati or Dayton, Ohio, metropolitan areas. Connected to a BIC FM-10 Beam Box indoor antenna, the Etude received 39 of those signals in listenable stereo (by listenable I mean that I could listen for an extended period without noise or interference driving me nuts). Using the same antenna, the HDT-1X listenably received 37 signals -- only two fewer than the Etude. Not bad for a tuner that retails for less than a quarter the price of the Magnum Dynalab in its day.

I then switched the Sangean to analog-only mode and did a lengthy comparison of the sound qualities of various analog local FM signals. The most revealing comparison was of the tuners’ reception of the lightly processed signal from our local classical public-radio station. Both tuners produced solid bass and an extremely sweet midrange. The only real difference was the Sangean’s insignificant extra bit of brightness at the highest registers of orchestral violins. Analog FM performance was nearly a draw between the two -- which you preferred would depend on whether you wanted just a touch more brilliance in your highs.

As for the differences between analog and HD reception, this will take some explaining:

Before standard analog signals are sent to the transmitting antenna and then to your radio, they’re subjected to processing. In the worst cases, the entire signal’s dynamic range is compressed to no more than 5-6dB, and equalized to enhance the midrange and deemphasize the bass and highs; at the same time, the output of the studio microphones is "brightened" so that the DJs’ voices will cut through background noise. And because of the phase shifts involved in such processing, soundstages are unstable. As a result, most stations sound as if their audio has been run through a stump grinder. Public radio stations, which have a higher regard for their listeners’ intelligence and hearing, tend to process their signals far less.

So far, HD signals can’t be subjected to drastic levels of processing -- they go too easily into distortion, and a distorted digital signal is all distortion all the time. (It’s that On/Off, Ones/Zeros analogy: a digital signal either isn’t distorted and sounds good, or it is distorted and sounds awful.) Even the analog stations that normally are the worst offenders back off on how much they process their HD signals. Thus, when an HD radio switches from analog to HD, the music sounds better, with a somewhat broader dynamic range (determined by the range of the source material) and a more open sound.

The result with the Sangean HDT-1X? For the first time in years, I could listen to several of the local commercial rock stations without grinding my teeth. That brought pleasure.

Here was another pleasure. An HD radio or tuner has, in effect, two receivers: the usual analog circuitry, and the far more complicated HD circuits. When an HD radio picks up an HD signal, it must link to that digital stream, which takes about seven seconds. During those seven seconds, the station’s regular analog signal is heard. As soon as the HDT-1X’s HD circuit took over, the highs blossomed forth -- the upper registers opened up and became airier. Bass drums in symphonic works were tighter, more like what I hear in concert halls. The mids remained silky and gorgeous, but I noticed far less background hiss -- it’s a different sort of sound than I’m accustomed to hearing from FM. The soundstage was tighter, from left to right and from back to front; the voices stayed put in front of me.

There’s also HD AM, but in my opinion, HD AM doesn’t offer HD FM’s potential of success. For one thing, no subchannels are available via HD AM. Second, the technology adds a lot of noise just off center channel to what is already a noisy band. Where I live, for example, the HD AM signal of one big station broadcasting at 700kHz AM causes interference on receivers from 660 to 730kHz. However, the analog side of the HDT-1X is decent for an AM tuner today, with the usual limited audio bandwidth, and decent sensitivity and selectivity -- just the thing for listening to talk radio.

Conclusion

What you get in the Sangean HDT-1X for your quarter-large ($250) is an analog tuner that will satisfy most dedicated radio listeners who are audiophiles. You also get the advantage of HD Radio, which delivers better sound than standard FM, as well as a lot of new, interesting programming. If you’re into radio listening, you owe it to yourself to try the HDT-1X.

But remember that HD Radio, like anything digital, is a switch -- it’s on or it’s off, with little middle ground. If the digital signal level isn’t strong enough, you don’t get interference, you get a dropout. And in areas where signals are weaker, they can drop in and out without warning. Broadcast engineers are about to propose some changes that will allow HD Radio signals to travel farther and stronger than they now can.

Don’t try to find a Sangean HDT-1X at your local big-box electronics store; they won’t know what you’re talking about. Go to www.hdradio.com or www.sangean.com to find dealers, most of whom are on the Internet. HDRadio.com often posts notices of rebates or special offers on HD radios, so it’s worth a look. But if you’re into radio at all, by all means investigate the Sangean HDT-1X.

...Thom Moon

Price of equipment reviewed


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