Every wireless carrier in the United States runs on radio frequencies it is licensed to use, county by county. Those licences are public. They are also spread across a database built for lawyers. A county page on carrierdepth is that database, redrawn so that you can read it in a minute.
Start with the four tiers
Radio spectrum behaves differently depending on frequency, and almost everything about a network follows from that.
- Low-band (below 1 GHz) travels for miles and passes through walls. It decides whether you have service at all.
- Mid-band (1 to 2.2 GHz) is the long-serving middle: PCS and AWS. Decent range, decent capacity.
- High-band (2.3 to 6 GHz) is where modern 5G speed comes from: wide channels, shorter reach. Many people call this "mid-band" too; we split it out because it behaves differently enough to matter.
- mmWave (24 GHz and up) has enormous capacity and a range measured in city blocks.
The number in each tier is megahertz: how much room the carrier has. More megahertz means more data can move at once. Twenty megahertz of low-band is a lot. Twenty megahertz of mmWave is a rounding error.
Then the band plan
The band plan is the picture. Each strip is one band, drawn to scale, left to right from lower to higher frequency. Each coloured block is one licence, and the colour is who controls it. Paired bands have two halves: the uplink, where your phone talks, and the downlink, where the tower answers. A gap between them is deliberate; it keeps the two from interfering.
Look for width and for neighbours. A carrier with three adjacent blocks can run one wide channel across all of them, which is faster and more efficient than three separate narrow ones. Contiguous spectrum is the quiet reason some carriers get more out of the same total.
Then the 5G band names
Your phone does not know what "Lower 700 MHz B block" means. It knows band numbers: n71, n41, n77. The second section of each county page regroups the same licences under those names, so you can match what a field-test screen shows to who is licensed there. If you have a channel number rather than a band, the decoder turns it into a frequency and a licensee.
Then, if you want it, every licence
The table at the bottom lists each block with its exact frequencies, the legal entity that holds it and its FCC call sign. Two columns deserve a note.
Licensee and lessee. The licensee owns the licence. A lessee has rented the right to use it. Schools and universities hold a great deal of 2.5 GHz and lease it to a carrier. We show both, and credit the spectrum to the carrier that leases it.
Licence area. Licences are not issued by county. They are issued by market areas with names like CMA, BTA and PEA, some smaller than a county and some covering several states. We map each one down to the counties it covers, including the awkward cases where a licence has been partitioned along a county line.
The one thing to remember
A licence is what a carrier may build, not what it has built. Treat a county page as the upper bound on each network, then check it against your own experience.