GMRS setup guides Range Planner
GMRS Range Planner Height, terrain and the radio horizon
Drag the sliders to see whether two GMRS stations can see each other over the curve of the earth, a ridge or a treeline.
Range Planner
Set both antennas, the ground under them and anything in the way. The path chart updates as you drag.
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My Setups
Geometry over a smooth earth, not a coverage prediction. Power, antenna gain, foliage loss and the radio itself aren't modelled; real range is usually shorter.
How the Planner Works
- Radio horizon: 1.41 × √(height in feet) miles for each antenna, the same 4/3-earth formula as our GMRS range guide (radio horizon). Ground you stand on counts as height when it sits above the land between you.
- Earth bulge: how far the earth rises into the path at each point, d₁ × d₂ ÷ (2 × the 4/3 earth radius). Over 8 miles it’s about 8 ft in the middle; over 30 miles, about 113 ft.
- Fresnel zone: the football-shaped space around the direct line, √(λ × d₁ × d₂ ÷ D) with λ = 2.13 ft at 462.6 MHz. Radio planners aim to keep at least 60% of it clear (Fresnel zone).
- What it leaves out: transmit power, antenna gain, receiver sensitivity, foliage loss and reflections. The FCC’s own figure for GMRS is “one to twenty-five miles depending on station class, terrain, and repeater use” (FCC).
Height wins. Doubling an antenna’s height adds about 41% to its horizon; going from 5 W to 50 W doesn’t move the horizon at all. To reach past it, use a repeater or a base antenna.
Plan the radios next with the Family Kit Builder.
What Changed
The latest additions and re-checks across the database.
Walkie-talkie gift guide with a Gift Finder: filter by who it's for, license and budget.
eCFR Part 95 Subpart E re-checked: still no change since Feb 10, 2026.
Radio finder on the comparison table: search, type, IP67, USB-C, NOAA and under-$50 filters.
New Best GMRS Radios page with eight quick picks drawn from the database.