Radio waves travel in straight lines
Line of sight
- GMRS works best when the antennas could almost see each other
- Hills, buildings and the earth's curve block the signal
- Trees and wet leaves soak it up
What that means
- Doubling power adds only a little range
- Raising the antenna adds a lot
- A hilltop beats an extra 5 watts every time
How far each antenna can 'see'
| Antenna height | Radio horizon | Example |
|---|---|---|
| 6 ft | About 3.5 miles | Handheld at head height |
| 15 ft | About 5.5 miles | Second-story window |
| 30 ft | About 7.7 miles | Mast on the ranch house |
| 100 ft | About 14 miles | Tall tower |
| 200 ft | About 20 miles | Repeater on a high tower |
Rule of thumb: radio horizon in miles ≈ 1.41 × √(height in feet). Add both stations' horizons for the most you could hope for over flat ground.
Putting it together
≈7miles: two handhelds on flat ground, at best
≈11miles: handheld to a 30 ft ranch mast
≈23miles: handheld to a 200 ft repeater
1–2miles: real life in hills and trees
These are best-case figures over flat, open land. Arkansas hills and forest cut them down sharply.
Remember
Before buying more power, get the antenna higher.
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Answer key
- GMRS signals travel mostly:In straight lines, like lightGMRS is line-of-sight; hills and the earth's curve block it.
- Which helps range the most?Raising the antenna higherHeight adds far more range than extra watts.
- About how far is the radio horizon for an antenna 6 feet up?3.5 miles1.41 × √6 ≈ 3.5 miles.
- The rule of thumb for radio horizon in miles is about:1.41 × √(height in feet)Add both stations' horizons for the best case over flat ground.
- What range should you plan on between two handhelds in Arkansas hills and trees?1–2 milesReal-world terrain cuts best-case figures down sharply.