Bob Witte KØNR
11 Dec 2016
Amateur radio operators on the VHF bands often use the Maidenhead Locator System for indicating their location, often referred to as a “grid locator.” A grid is defined by 1° latitude by 2° longitude, measuring approximately 70 × 100 miles in the continental US. A grid is indicated by two letters (the field) and two numbers (the square). For example, the home location of KØNR is located in grid DM79, which includes greater Denver. Greater Colorado Springs is to the south in grid DM78.
These things are commonly called grid squares even though they are really rectangles or perhaps trapezoids. (Actually, since the earth’s surface is curved, they are more complicated three dimensional shapes.) Anyway, I try not to say grid square, but it often sneaks in.
The most commonly used version of grid locator is the 4-character version (e.g., DM79), which is used for the major VHF contests and awards. Be aware that there is also 6-character version, which provides a more precise location. The 6-digit locator is used in some contests including the ARRL 10-GHz and Up Contest. The 6-character locater adds on two additional characters to the 4-charater version, so they are consistent and compatible. For example, my 4-character locator is DM79 and my 6-character locator is DM79nc. We’ll focus on the 4-character locator on this web page.
Finding Your Grid
If you know your latitude and longitude, you can use AMSAT’s conversion page to find your grid square more accurately. The ARRL has more detailed information on the Maidenhead Grid system. For a little more detail about how the grids are constructed, see EI8IC’s web page. In particular, this page shows how the additional two characters are determined to get the 6-character locator. K2DSL has created some of the most powerful tools on this useful web page for mapping out grids.
Map of US VHF Grids
Map of VHF Grids in Colorado
For locations in Colorado, the map shown below can be used to determine the grid.
Note: The map shown below is a rough approximation of where the grid lines are located. If you are near a grid boundary, you need to determine your grid via more accurate methods. In particular, note that the eastern boundary of grids DN80, DM89, DM88 and DM87 is 2 to 3 miles east of the Colorado state line.