In the decade since Sirius Satellite Radio and XM Satellite Radio applied for licenses, got their satellites into space, and then spent tens of millions on Howard Stern and Oprah Winfrey, the doubters have said only one company would survive. Recently, reports have surfaced that Sirius is offering to buy out XM. What does this mean to users and should you hold off buying a receiver, especially an XM receiver?

You don't have to be a wizard to suspect if there's just one satellite radio service, the current $12.95 monthly fee each charges now would go up. But if you can afford $12.95 a month, you can probably handle $15.95. Just forgo one Starbuck's coffee every four weeks.

HD Radio is a competitor that didn't exist when Sirius and XM signed their cross-my-heart-and-hope-to-die pacts with the government and promised they wouldn't merge. FCC chairman Kevin Martin recently said it's very unlikely they'd be allowed to merge, which either means that it's not going to happen, or that it's not going to happen before a lot more lobbying dollars get spent. I'm in the latter camp.

With all this in mind, here are some thoughts on the services in general and how a merger would affect the user.

Q: Aren't Sirius and XM the same?

A: Yes and no. Both have decades channels (1960s on Channel 6, 1970s on 7, etcetera), oldies channels, rock channels, deep-tracks channels, talk radio, a comedy channel, a really funny (read: dirty) comedy channel, Spanish channels, Christian channels, and so on. But Sirius has NASCAR, the NBA, and the NFL; whereas XM has Indycar racing, Major League Baseball, and the NHL. Sirius has Howard Stern; XM has Oprah Winfrey.

Q: Are they commercial free?

A: Yes and no. Satellite music stations mostly have no commercials; the other channels do. But the music channels run lots of self-promotional ads, which you and I would call "ads." Satellite is still better than traditional radio.

Q: Will Sirius and XM merge?

A: Sooner or later, probably yes. If they want to, they'll find a way.

Q: Is this good for the customer?

A: Not really, at least short-term. It would mean less competition, and rates would go up. In the long run, maybe it doesn't matter, because we'll be streaming audio over our cell phones or in-car WiMax connections.

Q: If my satellite service is the loser in the merger, is my satellite radio tuner worthless?

A: That's unlikely, at least not right away. The satellites (different ones for Sirius and XM) are up there, and there's more revenue to be had in keeping them active than in letting them go dark. Over time, you might see bridge radios that do both Sirius and XM, and then a decade or so from now there'd be a single signal.

Q: Should I hold off on buying a satellite radio tuner, especially an XM device?

A: Not at all. While the radio costs money ($50 to $150 for most add-on car modules), the real cost is the programming, about $150 a year, and that's something you're going to use and probably enjoy. As a worst case, suppose you buy the loser's radio, and it's off the air in four years (which is unlikely). You're out a $100 radio that's at the end of its life anyhow, and you've spent $600 on programming which you enjoyed for 48 months.

Q: What if I'm car shopping?

A: There you've got a small problem. Most every automaker sells one or the other service but not both, and they all have the same nonsensical response that their customers are happy with the single choice. Right. If you lease and turn over a car in 36 to 48 months, you've got no problem. But the guy who buys your used car might have a problem if, say, the car is XM-only, and the XM signal goes away. The second or third buyer could add an external tuner, but that's clunky (and a bit less safe, because of the smaller display located in a suboptimal position).

Q: What is HD Radio and what's multicasting?

A: HD stands for high definition radio, although it's not HD compared with traditional radio in the the way that HD TV is worlds better compared with standard-definition TV. "Static-free" would be an appropriate way to describe the digital signal; you're not going to think Zubin Mehta is conducting a tiny orchestra in the back seat. HD uses the same frequency as the analog signal; you get both the analog signal and the same programming in digital. That's simulcasting. If the HD signal gets lost, the radio switches to the analog signal, which usually has more range (and static). Newer HD radios add one or two additional programming feeds, still within the same frequency's bandwidth. That's multicasting (and it can be done because digital signals take up a fraction of the bandwidth used by the analog signal). It means that in New York City or Los Angeles, you could have more than 50 programs coming your way.

Q: Is HD Radio free?

A: Yes, there's no monthly fee, but it's not commercial-free. Some of the multicast feeds are commercial-free, but a reasonable appraisal is "commercial-free for now."

Q: Is HD Radio really a competitor for satellite radio?

A: Yes, if you live in a big metro area with a couple dozen stations and don't travel outside the region and lose the signal. I think you still won't have a wide range of programming on HD Radio, because the stations aren't going to sit down and say, "You do light classical and Dr. Seuss read-a-longs, I'll do the Latino dance and Lithuanian folkie channels."

Q: Does satellite radio have other competitors.

A: The iPod may be its biggest competitor now, especially in cars with iPod adapters that let you use the radio controls. And don't forget cars with hard drives in the dash that rip and store every CD you play, and the coming cars with USB adapters (such as the Ford Sync cars) that play any music player, not just the iPod, as well as USB keys with MP3s or WMAs.

Q: Is HD Radio expensive?

A: Some replacement car radios are well under $200, as are add-on HD Radio tuner modules. There are also HD tabletop radios and stereo receivers. The one automaker with a new-car HD Radio option is BMW, which charges $500, which is $95 less than they charge for Sirius.

Q: What's the right price for satellite radio or HD Radio?

A: Zero. OK, maybe $25 extra for satellite radio, free or $10 for HD Radio. That will happen, but not right away. When HD Radio hardware is ubiquitous, it will be a good deal for everyone; in that regard, HD Radio probably has a bright future.

Q: So HD Radio is a good deal?

A: Sort of, yeah. You're getting three times as much programming. Or three times as much crap. Maybe both.

Q: What would you buy?

A: I'd get a new car with satellite radio, so long as the price was lower than a $250 upcharge. If HD Radio is less than a $100 upcharge, I'd get that, too. I love satellite radio, and I think built-ins are vastly more versatile than add-ons. That said, I hop back and forth among FM radio, satellite radio, and my iPod. Sometimes I want to hear what someone else has programmed, and sometimes I want to hear what I want to hear.