US mobile frequency bands and what they mean for coverage
Low-band, mid-band, C-band and millimetre wave — the physics of why some signals travel miles and others stop at a window, and why a tower's height matters less than the frequency it carries.
Published 28 Aug 2026
The single most useful thing to understand about mobile coverage is that frequency and range trade off against capacity, and there is no way around it. A network operator choosing what to deploy on a given tower is choosing where to sit on that trade-off.
None of this appears in the structure register. But it explains most of what people find puzzling about coverage, so it is worth laying out.
The trade-off
Lower frequencies travel further and penetrate buildings better. Higher frequencies carry more data. That is the whole thing, and it follows from physics rather than from engineering choices.
Longer wavelengths diffract around obstacles and pass through walls with less attenuation. Shorter wavelengths carry more information per second because there is more bandwidth available up there — but they are absorbed and blocked much more readily.
The four tiers in the US
Low-band — roughly 600 to 900 MHz
The coverage workhorse. Bands here include 600 MHz, 700 MHz and 850 MHz.
A single low-band site can serve a wide area, and the signal gets inside buildings reasonably well. This is what carriers use for rural coverage and for the “nationwide 5G” claims in their advertising, because it reaches nearly everywhere.
The catch is capacity. There is not much spectrum available at these frequencies, so a low-band 5G connection is often no faster than good 4G. It is broad rather than fast.
Mid-band — roughly 1.7 to 2.5 GHz
The traditional backbone of 4G: AWS, PCS, and the 2.5 GHz holdings that became central to T-Mobile’s 5G network.
A reasonable compromise. Range is a fraction of low-band but the capacity is substantially higher. Most of the everyday mobile experience in suburban and urban America runs on mid-band.
C-band — roughly 3.7 to 3.98 GHz
Auctioned in 2021 and deployed hard since. This is where the genuinely faster 5G lives for most carriers.
Range is noticeably shorter — a C-band site covers perhaps a third of the area a low-band site does, which is why deployment required a great many new sites rather than just new radios on existing ones. Building penetration is meaningfully worse.
The 2021–2022 dispute with the aviation industry over radar altimeter interference concerned this band, which is also why some deployments near airports were restricted.
Millimetre wave — 24 GHz and above
Enormous capacity over very short distances. Gigabit speeds are real. So is the fact that a body, a tree or a window can stop the signal.
Deployed in dense pockets — stadiums, arenas, downtown blocks — and essentially useless as area coverage. If you have ever seen a spectacular 5G speed test and been unable to reproduce it twenty metres away, this is why.
What this means for a tower on a map
A structure page on this site tells you a height and gives you a radio horizon estimate from it. That estimate is the ceiling under ideal conditions. Where a site actually lands relative to that ceiling depends almost entirely on frequency:
| Band | Realistic share of the horizon figure |
|---|---|
| Low-band, rural, flat | most of it |
| Mid-band, suburban | perhaps a quarter |
| C-band, urban | a small fraction |
| Millimetre wave | negligible |
A 60-metre tower has a radio horizon around 32 km. Running low-band in flat country it might genuinely serve much of that. Running C-band in a city it might serve a kilometre.
Same tower. Same height. Same number on the page.
Why the register cannot tell you
Structure registration is an aviation matter. It records the physical object. The radios mounted on it are licensed separately, under a system that is not linked to the structure record in any way you can query — and in many cases the spectrum licence is held for a whole geographic market rather than tied to individual sites at all.
So there is no path from “this structure exists at these coordinates” to “it transmits band n77 at this power”. Anyone claiming otherwise from public data is guessing.
The practical version
If you are trying to work out why coverage at your address is what it is:
- Good outdoors, bad indoors → probably mid-band or C-band, and your building is the problem
- Bad everywhere, rural → probably genuinely distant from any site
- Full bars, unusable data → congestion, not coverage
- Excellent in one spot, gone twenty metres away → millimetre wave, or you have found the edge of a sector
None of these are answerable from a structure database. All of them are answerable by walking around with the phone, which is unglamorous but works.