What the Maidenhead locator is
The Maidenhead locator (QTH locator or grid square) summarises a position in a few characters for amateur radio contacts and contests. The first two letters (field) split the world into 20° × 10°, the next two digits (square) into 2° × 1°, and the third pair (subsquare) into 5′ × 2.5′, about 7 × 4.6 km at New York's latitude. ARRL headquarters in Newington, Connecticut is in FN31pr.
Frequently asked questions
How many characters should I give?
Six is the norm on VHF and UHF contacts; four are enough on HF. The fourth pair is only used on microwave bands and satellites.
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