How to read an FCC antenna structure registration

An Antenna Structure Registration record is a short, dense thing. It has a number, a set of coordinates, a couple of heights, a structure type code and an owner. That is nearly all of it. Once you know what each field means — and, more usefully, what each field does not mean — the record tells you a surprising amount.

The registration number

The registration number, usually written as an ASR number, is the stable identifier. It stays with the structure through ownership changes, height changes and rebuilds. If you want to look something up at the source, this is the key you use. Every structure page on this site shows it prominently for exactly that reason.

It is not a licence number. A registration says a physical structure exists and has been cleared with the FAA where required. The radios mounted on it are licensed separately, under a different system, and those licences are not linked to the ASR record in any way you can query easily.

The two heights, and why they differ

Every record carries several height fields, and confusing them is the single most common mistake.

Height of structure above ground is the supporting structure itself — the steel, the concrete, the mast.

Overall height above ground includes everything mounted on top: antennas, lightning rods, any appurtenance that adds to the total. This is the number that matters for aviation, and it is the one this site displays.

Ground elevation above sea level is the elevation of the site itself.

Overall height above sea level is the previous two added together.

That last relationship is a useful check. If ground elevation plus overall height above ground does not equal overall height above sea level, something in the record is wrong. Across the current national file of 197,269 registrations, only 22 fail that test — about one in nine thousand. The data is clean.

Heights are filed in metres. American readers usually want feet, so this site shows both.

Structure type

The structure type is a short code, and there are 174 distinct ones in current use. Five of them account for ninety per cent of everything built:

• TOWER — a freestanding tower, construction unspecified
• LTOWER — a lattice tower, the open steel framework you picture when someone says “radio tower”
• MTOWER — a monopole, a single tubular shaft
• GTOWER — a guyed tower, held up by tensioned cables
• POLE — a pole of unspecified construction

The rest is a long tail that gets genuinely interesting. There are registrations for water tanks, smokestacks, silos, bridges, oil rigs, billboards, and trees — the last of which means a structure disguised as a tree, not an actual tree.

There is also a family of codes like 2TA1, 3GTA2 and 4TA3. These denote one element of a multi-tower array: 3TA2 is the second tower of a three-tower array. Almost all of these are AM broadcast antennas, where several towers work together to shape the signal in a particular direction rather than radiating equally all round.

Owner — the field most often misread

The owner field is the entity that registered the structure. On more than half of all registrations that is a tower company: American Tower, Crown Castle, SBA, Vertical Bridge and their many subsidiaries.

Tower companies do not operate wireless networks. They build and own structures, then lease space on them to carriers — often several carriers on the same tower. So the owner field tells you who owns the steel. It does not tell you whose network you are connecting to, and there is no field in the ASR data that does.

This trips people up constantly. Someone searches for “Verizon tower near me”, finds the structure, and sees it registered to American Towers LLC. Both facts are true at once.

The subsidiary naming makes it worse. Crown Castle’s registrations appear under CCATT LLC, Crown Atlantic Company, Crown Communication and Pinnacle Towers, among others. Verizon’s appear under Cellco Partnership. None of those names contain the parent brand.

Status

Only structures with a status of Constructed are shown on this site. The full file also contains registrations that are granted but not yet built, and ones that have been terminated. Including them would mean showing people towers that do not exist, which is worse than showing them nothing.

That filter cuts the national file from 197,269 registrations to 141,647 constructed structures.

What is not in the database at all

This is the important part, and it is the reason a lot of people conclude the data is wrong when it is not.

Registration is generally required for structures over 200 feet, and for shorter ones near airports where they might affect aviation. Everything below that threshold, away from an airport, does not need to register and mostly does not appear.

In practice that means the ASR file misses:

• Small cells on utility poles and streetlights, which is where a great deal of recent urban capacity has gone
• Most rooftop installations
• Short masts on commercial buildings
• Anything indoors — distributed antenna systems in stadiums, malls, office towers

So if you look up your neighbourhood and find nothing, that is not evidence there is no coverage equipment nearby. It is evidence there is no registered structure nearby. Those are different claims, and the gap between them has widened as networks have densified with smaller equipment.

Dates

The construction date is when the structure was built, as filed. Registrations are updated when something changes, so a record reflects the most recent filing rather than continuous monitoring. A structure registered in 1997 and never modified since will still show 1997.

Where to check

The FCC’s own Antenna Structure Registration search is the authoritative source. Every structure page here carries the ASR number so you can look it up directly. If a figure on this site disagrees with the FCC’s record, the FCC is right and we have a bug worth telling us about.