Questions about GMRS

[Guest Dwayne]

I have a question: How far will GMRS reach I have two son-in-laws that live two to three miles away from me one north one south in Hickory Grove SC there are many trees and some hills will GMRS reach?  We are looking for away to talk on radios.  

[wayoverthere]

There's a lot of factors that affect the answer, so it isn't quite an easy yes or no. With no obstructions, a lot further is possible, but gmrs (and UHF as a whole) is very much line of sight.  Getting a good antenna up where obstructions are minimal will help, as will power to some extent (especially with the foliage part of the equation). Big hills may be problematic, though, and some areas are more restricted than others about setting up antennas.

In relatively clear air (antenna in my attic) and 50 watts, I can reach a repeater a little over 60 miles out (that sits around 3000 ft up in the foothills) and another 30 or so miles the opposite direction at 5000 ft. The ratings shown on a lot of the "bubble pack" radios represent ideal conditions, which is why they include "up to" in the small print when they talk in miles of reach.

[michael95472]

Few miles should be no problem with a 15 watt base type radio and a decent antenna.
If you’re thinking of a handheld, it depends on what’s between. Hills, buildings, and the sort degrade signal. 
if there is a repeater in your area then it’s no problem. 

[mbrun]

I agree with what wayoverthere and michael before me said, so it does depend. The only way to know for sure in you environment is to test it. The terrain and the density of trees and buildings (aka obstacles) are the major factors.

I have never had a case where HT to HT did not work at least 1/2 miles. That is my personal minimum in outdoor use over 20 years. The theoretical max distance of HT-HT communications between two people standing on a perfectly smooth round earth without trees, buildings and other obstructions would around 6 miles. However, when one uses a radio with an external antenna that is raised above high above the roof-line, range nearly always increases. The theoretical distance increases commensurate with height, as does the real-world distance.

I my case, I have a GMRS high-gain antenna mounted at 40’. At that height I have reasonably reliable communications with mobile units around me out to about 3-4 miles with hit-n-miss communications in different directions out to about 7-8 miles. When I raise the antenna to 56’, my range numbers increase by several miles in all directions. If I could get the antenna above the tree line my range would increase further.

Putting it into context. I live in area I estimate is 60% trees and a mix of homes, light commercial, and fields. Terrain is mostly flat to mildly rolling. My home is located at near the highest elevation in the immediate area.

Hope this helps.


Michael
WRHS965
KE8PLM