By purchasing MetroPCS, T-Mobile will get enough spectrum to install fast LTE in highly populated areas. This map shows where.

Spectrum is the lifeblood of wireless carriers, and it's one of the major reasons . As they explained in their merger announcement this week, the two carriers each have much less spectrum than their bigger competitors, which makes it much harder for them to set up speedy 4G LTE networks that really face off against Verizon's and AT&T's.

As data sent to us by Mosaik Solutions shows, combining the two carriers will make them much stronger in highly populated areas (as well as in a few outliers like Montana), though it won't change the game nationwide. MetroPCS's spectrum holdings give T-Mobile much more depth in corridors stretching from Vermont to Philadelphia, Atlanta to Miami, the Northwest, and the area around Dallas.

, which should improve its position in Kansas City.

Remember, though, that spectrum is only half the battle. The companies need to build out their networks as well. So while the combined network may theoretically be able to cover Montana, the company may not find it worthwhile to plant towers all across Big Sky Country.

Take a look at the graphic below to see how MetroPCS plus T-Mobile equals a carrier that may be very strong in the Northeast, Southeast (especially Florida) and California.

For more, see PCMag's explanation of how the merger could affect both and customers, as well as .