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Grid squares and UTC — edited Aug 31, 2026 by Unknown editor
This is the first recorded version, so every line is shown as added. Note: Imported from content/wiki
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Two conventions turn up in every log, every digital mode and every award program: the Maidenhead grid
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locator, and Coordinated Universal Time.
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## Maidenhead grid squares
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A grid locator compresses a latitude and longitude into a few characters, precisely enough for
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antenna aiming and distance scoring:
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- **Field** — two letters, an 18 × 18 division of the globe in 20° of longitude and 10° of latitude
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(`EM`).
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- **Square** — two digits inside that field, 2° of longitude by 1° of latitude, roughly 70 × 100
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miles in the continental US (`EM66`). This four-character form is what VHF contests and FT8 use.
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- **Subsquare** — two more letters, about 3 × 4 miles (`EM66kn`). Used for microwave work and
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precision aiming.
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- Longer forms exist (`EM66kn32`) and are used for millimeter-wave and rover operations.
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Look yours up once and write it on a card by the radio; QRZ.com, several phone applications and the
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ARRL's grid-square lookup will all convert an address. Grids are how VHF and 6 m contests score
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(multipliers per grid), how FT8 reports distance, and how the VUCC award counts credit. See
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[VHF and UHF operating](/wiki/operating/vhf-uhf-operating) and
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[weak signal, scatter and moonbounce](/wiki/operating/weak-signal-and-scatter).
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Do not confuse a grid square with a **CQ zone** (used by the CQ contests and the WAZ award) or an
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**ITU zone**; DX contest exchanges may ask for either.
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## UTC, and why your log uses it
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Amateur radio is worldwide, so a single reference time avoids arguments about whose Tuesday a contact
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happened on. That reference is **UTC**, spoken as "zulu" and effectively the same as the old GMT.
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- Log **date and time in UTC**, always. Contest logs, LoTW matches and QSL confirmations are checked
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against it, and a contact logged in local time will fail to match.
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- The UTC day rolls over at 7 pm Eastern Standard Time — which means an evening contact belongs to
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**tomorrow's** date in the log, the single most common logging error there is.
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- Set the shack clock to UTC and leave the wristwatch local; set the logging computer's clock from
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an internet time source, because digital modes such as FT8 need to be within a second or two to
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decode at all.
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- Contests, nets and band openings are announced in UTC. "0000Z Saturday" is Friday evening in the
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US.
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| Time zone | Standard | Daylight |
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|---|---|---|
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| Eastern | UTC−5 | UTC−4 |
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| Central | UTC−6 | UTC−5 |
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| Mountain | UTC−7 | UTC−6 |
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| Pacific | UTC−8 | UTC−7 |
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| Alaska | UTC−9 | UTC−8 |
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| Hawaii | UTC−10 | (no DST) |
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UTC does not observe daylight saving time, so the offset from your local clock changes twice a year
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even though UTC does not.