How to read a Maidenhead grid locator
Amateurs give their position as something like JN54tu rather than as two decimal numbers. It is shorter to say over the air, it is precise enough for any purpose on VHF, and the amount you give says how precise you are being.
How it is built
The globe is divided into 18 by 18 fields, lettered A to R, starting at the South Pole and the 180th meridian. Each field is 20° of longitude by 10° of latitude. Each field is then divided into 100 squares numbered 00 to 99, and each square into 576 subsquares lettered aa to xx.
| You give | Example | Precision |
|---|---|---|
| Two characters — the field | JN | about 1,500 km |
| Four — the square | JN54 | about 100 km |
| Six — the subsquare | JN54tu | about 5 km |
Six characters is the normal courtesy on VHF and enough to point a beam. Four is enough to say which part of a country you are in.
Why not latitude and longitude
Because a locator is readable aloud under noise, and because the distance between two of them is easy to work out. Contest scoring, propagation records and beam headings all run on grid squares, so the whole vocabulary of VHF operating is built around them.
The convention is capitals for the field, digits for the square, and lower case for the subsquare — JN54tu, not JN54TU. Nobody will correct you, but it is how it is written.