Maidenhead Grid Squares Explained — How to Read FN20xr, PM95, etc.

Maidenhead Grid Squares Explained — How to Read FN20xr, PM95, etc.How Maidenhead grid squares encode latitude and longitude — fields (AA-RR), squares (00-99), subsquares (aa-xx). Used by every ham operator for QSO exchange and beam-heading calculation.Maidenhead is the worldwide grid-square system every ham operator uses to identify station location. It's a hierarchical alphanumeric encoding of latitude and longitude — short enough to say on the air, precise enough to point a directional antenna at.How it worksThree nested levels of subdivision:

Field (chars 1-2) — Letters A-R. 18x18 fields, each 20° lon x 10° lat. "FN" covers most of US northeast.

Square (chars 3-4) — Digits 0-9. Each field is 10x10 squares of 2° lon x 1° lat. "FN20" is NYC area.

Subsquare (chars 5-6) — Lowercase a-x. Each square is 24x24 subsquares of 5' lon x 2.5' lat (~5x2.5 km). "FN20xr" pins NYC to ~5 km.

Extended (chars 7-8) — Digits 0-9 (~500 m precision). VHF/UHF contesting only.

How operators use itSix-character grids are the standard — short enough to exchange in a contest, precise enough that beam-heading lands within antenna lobe width. Four-character common in HF QSOs. Eight-character for very precise VHF/UHF / EME / contest work.Part of the BloomWX learn library — beginner-friendly explainers covering every surface of the BloomWX weather dashboard. Open BloomWX to see live data for any U.S. county.