Digital Mobile Radio Sounds Awful

Somewhat obscure geeky things that other ham radio operators generally overlook tend to interest me.

It’s one reason I bought a 900 MHz transceiver at the Puyallup swap meet last month; it’s a band with almost no equipment built and marketed to ham radio operators. It took some searching to find something suitable (in this case, an HT marketed to business and government users which could be unlocked and programmed on that amateur radio band).

Probably for the same reason, DMR (Digital Mobile Radio, commonly known by its Motorola trademark MOTOTRBO) piqued my interest. Unlike 900 MHz (which is very quiet), there’s actually a smattering of operators using that mode on the 70cm band.

The downside is that the audio sounds positively awful (I’ve been listening to it on the net here). Think cheezy sci-fi voice effects from the 70s, sometimes so heavy that one must strain to hear what is being said.

Maybe it shouldn’t have come as a complete surprise. Unlike digital home entertainment audio, greater fidelity was never a goal for DMR. Instead, the goal was to cram as many channels into as little radio spectrum as possible.

If that’s your main goal, quality is going to suffer. There’s nothing particularly magic (or evil) about digital technology in this regard; one can use analog techniques to compress signal bandwidth, and those have a negative effect on audio quality as well.

I haven’t done much listening to it, but I’ve heard the “official” digital protocol for amateur radio in the VHF and UHF bands, D-Star, suffers similarly.

I think the chief upshot of this awful sound is that we cannot expect any such digital mode to last nearly as long as analog voice modes have lasted. As technology improves, ways will be found to make audio suffer less as it is compressed into a digital signal. It still won’t be high fidelity, mind you, but it won’t leave the listener straining to discern speech, either.

Because of present poor audio quality, the high likelihood of rapid obsolescence, and the significantly higher cost of digital over analog, digital voice is unlikely to be more than a bit player on the ham bands in the near future.

To that can be added adoption issues. A business licensee is a single organization; it can decide to go digital, make the investment in equipment, and issue all employees new radios. We amateur radio operators are individuals making individual choices; this creates a high path dependency in favor of the status quo.

Moreover, the commercial and public service bands are much more congested, so being able to cram in more signals is more important there. Even so, I wouldn’t expect present-day digital technologies to have comparable longevity to, say, analog FM.

HD Radio is the Quadraphonic Stereo of the 2010’s

After having listened to HD broadcasts regularly for about a month, that’s the inevitable conclusion. It’s there, stations have spent a lot of money on enabling themselves to broadcast it, but consumers have almost universally not adopted it and even broadcasters don’t take it very seriously anymore. Ergo, it’s going to die in the not-too-distant future.

Exhibit A: Knowing that the chips which decode HD into audio are proprietary, I wondered just how pricy they might be. After a bunch of Google searching (the magic keywords have slipped my memory and I can’t furnish a link at the moment, sorry), I found out that the fee is around $50 per chip. The receiver I purchased from an Amazon storefront was made several years ago, came to me new in its packaging, and cost me $40. In other words, HD receivers are not selling and are being liquidated at below cost.

Exhibit B: KING-FM‘s HD signal went off the air for a few days in the wake of last month’s ice storm. There was never any announcement to this fact on the air, or for that matter on KING-FM’s web site. By contrast, if they lost their analog stereo subcarrier, I find it inconceivable that there would not be both regular on-the-air announcements and a mention on their web site about it.

Moreover, I listen somewhat regularly to “the Evergreen Channel,” the program that airs on KING-FM’s HD2 digital subcarrier. Whenever they solicit listener contributions, they instruct you to “click the donate button on your player.” Never is any mention made of what listeners on HD radio should do; there is a presumption here that those of us who listen on HD are such a small minority that we’re not worth worrying about.

Exhibit C: For the past month or more, the HD subcarrier has been absent from the KUOW2 transmitter on 91.7 kHz, as evidenced by the following message on their web site:


We apologize for the break in our KUOW2 HD services. Our engineers are working to fix the problem.

Hey, at least they rated HD worth a mention on their web site; that’s more than one can say for KING-FM. But, to reiterate, it’s been this way for at least a month (i.e. ever since I’ve been trying to receive an HD signal from that transmitter). Obviously, it’s not a very high priority item for their engineers. Again, I find it inconceivable that they would take such a long time to restore the analog stereo subcarrier to their transmitter.

I would not be surprised, in fact, if KUOW decides to simply forget about HD on their second transmitter and if in a few months all mention of HD one day simply vanishes without explanation from the web page for that transmitter. That’s probably what’s going to happen to the vast majority of HD broadcasts in the coming five years or so: they will continue until something breaks in the station’s HD hardware, at which point it will be pronounced by management as not worth spending the money to fix and the service will be silently discontinued.

To reiterate, this will not be a surprise when it happens.

First, consider the cost: I would not have paid several hundred dollars for such a receiver. The only reason I purchased one is that I have a crappy slow Internet connection and cannot reliably stream audio. It was worth a one-time expense of $40 to have unlimited access to the BBC. At several hundred dollars per receiver, I would have just paid for better Internet service. That would cost a more, sure, but I’d then be able to stream audio from more than just the BBC, as well as watch videos on demand.

Second, consider the reliability: HD is still considerably more temperamental than analog FM, which is temperamental enough on an inside antenna: one is continually having issues with multipath interference and loss of signal strength causing loss of the stereo subcarrier. But at least with analog FM, one still gets an audible signal when that happens. With HD Radio, the signal suddenly and with no warning whatsoever vanishes completely. At least at home it’s possible to erect a good external antenna on the roof. In a car, you’re simply stuck with a small whip, and you will hit weak-signal areas as you drive around. It’s no wonder automakers have avoided adding HD Radio to the receivers they install in vehicles.

Finally, consider the improvement in sound quality: It’s very modest. Frequency modulation was designed to offer better sound quality than amplitude modulation, and it succeeds admirably in this regard; the difference in audio quality between an AM signal and an FM one is profound. In contrast, it’s difficult for me to discern any such difference between analog FM and HD Radio.

So I fully expect my $40 investment to become an interesting conversation piece about a mostly forgotten era in radio broadcasting in the decades to come.

HD Radio Revisited

I’m beginning to suspect my prior (and to some degree, current) experiences are a victim of the Connector Conspiracy. When I made a new antenna cable using parts salvaged from a defunct cell phone headset, I had much better luck receiving HD signals.

It’s still not perfect; reception drops out every so often and stays that way until I reseat the antenna connector. This makes me suspect that JVC deliberately chose to use a somewhat nonstandard 3.5 mm connector, one that fails to mate well with anything but the connectors on their (overpriced) accessory kits.

It is at least a partial fix, one that’s good enough to enable me to receive the BBC static-free on one of the digital channels of a KUOW. That will come in handy on the next big news day (forget about the Internet when a big story breaks; any streaming programming instantly becomes overloaded to the point of uselessness in my past experience).

The King is Dead, Long Live the King

Of course I made a point to listen to (and record) Voice of Korea today. The executive summary of the broadcast is given in the title; the “news” pretty much followed that summary to a ‘t’, segueing from an eulogy of the “Great Leader” to praise for the “Great Successor”.

Unwittingly, the station in that land of shortages and hardship for the vast majority of its people also gave Kim Jong-Il a most appropriate send-off, being interrupted twice by power cuts. At least, that’s what I assume they were because both transmitters went off the air simultaneously each time.

The edited (I deleted the static during the total of 11 minutes and 46 seconds of dead air in the two interruptions) audio may be found here. If for some reason you want to hear everything in real-time, breaks in transmission and all, that audio may be found here.

Note that if you’re not that interested in hearing the two praise songs (one to Kim Il-Sung, one to Kim Jong-Il) that start each broadcast, the main “news” broadcast starts about 7 minutes and 50 seconds in.

HD Radio: A Big Disappointment

Having noticed how local public radio station KUOW has some interesting-sounding programming on their HD radio subchannels, I did a little Google searching and found an HD tuner (new in the box) being offered for the somewhat astounding sum of $40. I did some research on the seller, and found her to be highly rated, so I decided to order it as a Christmas present for myself.

I was somewhat floored to find a box containing my purchase sitting on my doorstep this afternoon. I had not paid extra for rush shipping, and the quoted delivery time for non-rush shipping was as much as 4 weeks in the future. And it was as described: new, in unopened packaging.

Alas, HD radio itself proved to be as big a disappointment as the vendor who sold it was a pleasant surprise. HD is a subcarrier-based system, so it works basically like stereo FM signals: only the stronger signals present solid stereo reception, and only the stronger signals come in on HD. But, HD is even more fussy than the stereo subcarrier; you need a really solid, strong signal to get HD. Forget any sort of indoor antenna, you need something on the roof.

The only station I could reliably get in HD with an indoor antenna was the one I could care the least about receiving: the local right-wing Christian station. I had no luck getting an HD signal for KUOW, despite being able to get a fairly solid stereo signal on that station with an indoor antenna.

It’s presently not worth my scarce time and money to fuss with erecting an external antenna on the roof, particularly such a steep roof as the house I’m currently residing in as. So much for that experiment; glad I didn’t throw more than $40 at it.

Unidentified Pirate, 0045 UTC, 2011-12-05

A few days ago, I went on a brief test “DXpedition” to an area about 1/3 of a mile south from where I live. It’s an open area without many buildings or power lines not far from the summit of Seattle’s highest hill. I thought it might offer better listening conditions. I was right; the noise floor is dramatically lower than it is here.

While there, I ran across this signal (almost certainly a pirate broadcaster, given the frequency and time) on 6925 kHz at about 0045 UTC:

Unidentified signal