The LG V30 is coming to T-Mobile on Oct. 13, and it will be the first phone that runs on the carrier's new 600MHz network, also known as LTE Band 71.

T-Mobile bought a nationwide swath of this spectrum earlier this year for $8 billion, and has already begun building it out. The idea is to fill in the final gaps in T-Mobile's rural coverage.

Where did Band 71 come from?

Remember UHF TV? This was channels 38-51.

What phones use Band 71?

At the moment, the LG V30 is the only phone supporting Band 71; T-Mobile promises a Samsung phone by the end of the year. The Pixel 2 won't have it, nor will the iPhone X. We'll see more phones with it next year, and it'll be on all new T-Mobile phones by the end of next year, except maybe the iPhone. Apple follows its own rules.

So, does that mean I shouldn't buy an iPhone?

Not if you already have decent T-Mobile coverage, and you tend to go places with T-Mobile coverage. Band 71 is about covering rural areas where T-Mobile doesn't have coverage yet.

Will band 71 make T-Mobile viable in rural areas?

T-Mobile is already viable in a lot of rural areas. If you haven't checked out its coverage in the past year, it's expanded a lot. Take a look at our story, A Peek into T-Mobile's Massive LTE Growth, for more. Especially between 2015 and mid-2017, T-Mobile's rural coverage massively changed. Band 71 will help further.

Where is T-Mobile installing Band 71?

Right now, it's in Cheyenne, WY, and Scarborough, ME. Those towns already have T-Mobile coverage; the point is for T-Mobile to be able to test its Band 71 equipment in a real-world context without making too much of a splash.

Before the end of 2017, T-Mobile has promised to install Band 71 in parts of Wyoming, Northeast and Southwest Oregon, West Texas, Southwest Kansas, the Oklahoma panhandle, Western North Dakota, additional areas of Maine, Coastal North Carolina, Central Pennsylvania, Central Virginia, and Eastern Washington.

T-Mobile sent us two maps for its end-of-2017 coverage: one with Band 71 and one without. Comparing the maps, it looks like northern Wisconsin and Michigan; the Dakotas; and rural Missouri and Kansas will initially get the Band 71-only treatment.

What could hold it up?

Existing TV stations are relocating out of the band in 10 phases between now and July 2020. T-Mobile has to wait for the TV stations to vamoose to build out the new network. Many stations are evacuating ahead of their deadlines, though.

Also, if T-Mobile merges with Sprint and disappears up its own rear end figuring out how to reconcile the two businesses, all timelines are off.

How fast is Band 71?

In most of the country, T-Mobile has either 15+15 or 20+20 MHz of spectrum, which should deliver good speeds, but it depends on how far apart T-Mobile puts the towers. We think 10-20Mbps will be the norm. Band 71 can't yet be "aggregated" with other bands to provide super-fast connectivity, but that will come on new phones next year.

What's the Band 71 experience like now?

Pretty low-key. Almost everyone in Cheyenne and Scarborough will be on T-Mobile's faster Band 2 and 4 networks. It might extend T-Mobile into some buildings and cellars in those areas, but the real "green field" rollout hasn't happened yet.

In areas with existing coverage, "customers will see benefits similar to our 700MHz Extended Range deployments, like coverage that travels twice as far and works four times better in buildings," T-Mobile says.

Is all of T-Mobile's new coverage Band 71?

Not until the end of this year. T-Mobile is still building out Band 12 in "a few remaining areas" between now and December, the carrier tells us. Band 12, which T-Mobile calls "extended range LTE," has similar characteristics to Band 71, but it's supported on almost all phones sold right now, including iPhones.

Taking two examples, T-Mobile has Band 12 licenses it hasn't built out in far upstate New York and in Montana. (It relies on roaming partners in both areas.) If it builds out new coverage in either of those places, it might be band 12, not band 71, so you might not need a new phone. But if your area doesn't have Band 12 by the end of the year, you'll probably need a Band 71 phone for any new coverage, if I understand correctly what they're telling me.

What else is happening coverage-wise?

We've been waiting all year for T-Mobile to close a big deal with U.S. Cellular, which could greatly improve T-Mobile's LTE coverage in the Midwest. That wouldn't help people who live there and want to subscribe to T-Mobile—it's a roaming agreement—but it'll improve service for T-Mobile subscribers traveling through. We've heard it's stuck on technical integration involving voice-over-LTE systems, but they're working it out.