Tech Q? Satellite Radio

HD, DAB, SAT, a forest of abbreviations that all lead to one clearing -- Digital Radio. Leaving aside the woodsy analogy, (since it goes no further than that, really) here is Radio 2's Resident Geek Peter Cook with the weekly Tech Q? column, clarifying any number of issues about SAT. Over to you, Peter:

On Tech Q we're in the midst of a series about "digital radio" in its various forms: HD Radio, satellite radio, and DAB. Of all the forms of digital radio, the one format you have heard the most about is almost certainly satellite radio. In fact some of you may subscribe to satellite radio.

Just to be clear I'm only going to talk about the direct to consumer satellite radio systems and only those available in North America.

XM Satellite Radio launched in the US in 2001, SIRIUS Satellite Radio in 2002. Canadian divisions of both companies launched at the end of 2005 following CRTC approval. There's some background information about how satellite radio came to Canada at wikipedia.

Standard Broadcasting and the CBC are partners with SIRIUS in SIRIUS Canada. Canadian Satellite Radio has a partnership with XM to form XM Canada.

Remember that AM/FM stations (and indeed HD Radio stations) broadcast their signal from transmission towers.

By contrast satellites beam their signal down from high above the earth. The signal is picked up by the antennae on a car or attached to a receiver in your home.

Advantages

The primary advantage of satellite radio over terrestrial radio is the range of programming available. It is technologically impossible to squeeze over 100 channels into the (AM/FM) dial where you live. And when you drive out of range of your favourite FM station, it's gone.

SIRIUS and XM can blanket continental North America with their signals and provide lots of variety. So you can drive from St. John's to Victoria and listen to exactly the same station the entire way be it CBC Radio 3, 70's on 7 ("'70's Pop Hits"), or Road Dog Trucking ("Just for Truckers").

The music channels on satellite radio are currently commercial free.

Satellite radio offers text information related to what you are hearing. You can the read the name of the artist and song/music you are listening to.

As with other digital systems there is a potential for better sound quality than analogue broadcasts. Digital signals are more robust. The sound doesn't fade or fill with static. In general it either works or it doesn't. But if the data rate is too low, the sound can come up short compared to FM and even AM in some situations.

Disadvantages

If you want to hear satellite radio you need to purchase a special receiver, pay an activation fee and then pay a monthly subscription fee. This is not free, over the air terrestrial radio. The model is more akin to cable television where you pay money for more options.

There is no 'local' programming. Everyone, everywhere gets the same signal off the satellite so there's no room for the local news from a small city.

Choice vs Quality

Think of the signal beamed down from the satellite as a large pipe of fixed dimensions. Satellite radio broadcasters can push whatever they like through that pipe until it fills up. To attract subscribers they fill the pipe with as many channels as they can. More choice = more potential subscribers.

But there is a trade off. Each one of those channels takes up a certain amount of space in the pipe. As you add channels, the sound quality goes down.

No CBC Radio 2 on Satellite Radio?

No. Getting the satellite radio business off the ground in Canada involves a crazy balancing act. Remember that the same signal is beaming down from the satellites all over North America. There is going to be a limited amount of room for Canadian programming.

At the same time the CRTC would not have granted a broadcast license for anyone had they not met certain requirements: minimum number of Canadian-produced channels relative to foreign channels, a high rate of Canadian content on those channels, a certain percentage of French language programming, and a certain percentage of up-and-coming Canadian artists.

And remember what I said about choice vs quality. When you balance all of these factors there is not enough room on the satellite to host another music channel.

Audio Formats

XM uses the Coding Technologies' AACplus codec. (Recall that "codec" is short for "encode-decode". MP3 is an example of a different audio codec.) That codec is related to AAC but was designed for low bit rate applications and has since been superseded by HE-AAC. XM uses bit rates varying from 4 (!) kilobits-per-second for spoken-word traffic reports to 64 kbps for some music channels.

Apparently SIRIUS use the Lucent PAC codec. This is an older codec which works well at moderate bit rates but falls off in performance at lower bit rates. This gives SIRIUS less ability to drop to extremely low data rates. As for what Sirius actually deliver, I found conflicting reports in discussion forums and nothing at all official looking.

That means we have two incompatible satellite radio infrastructures.

Satellite Radio Business

You've probably heard about some of the upheavals in the satellite radio business. Both XM & SIRIUS signed high-profile and very expensive personalities to their services in an effort to attract customers to the services. It did that and got them lots of publicity (Howard Stern, US$100 million/year!). But there probably never were enough customers to support both companies and in the US the companies merged in mid 2008.

We all know what's happened to the economy since then. New car sales (the best bet for getting customers into satellite radio) have collapsed and consumers are cutting expenses.

The new company Sirius XM Radio was on the verge of bankruptcy by February of this year. Previously the company had been able to roll over it's enormous debt without any trouble but that became impossible in a market with an extremely tight money supply.

Even though the Sirius and XM have merged in the US, they still provide two services with incompatible radios receivers, satellites and production facilities. To add to the confusion, the separate companies in Canada have not merged. This story is a long way from over.

Next time on Tech Q I'll talk a bit more about the challenges facing satellite radio and about sound quality. In the meantime I know that some of you have personal experience with satellite radio as customers. Feel free to share your experiences.

As always, the opinions expressed in Tech Q are my own and not those of the CBC.