CB radios

[deserteagle71]

ALL the radios mentioned in this post are essentially line-of-sight. In other words, if there is a hill or mountain between two radios, there is small chance they will be able to talk to each other unless there is a repeater on top of the mountain to relay the signal. Signals CANNOT travel through earth! (Although in the right terrain and in certain cases, the signals may "bounce" around and get around obstacles that way.) Even heavy tree cover can attenuate a signal.

We use HAM radios in our Search and Rescue unit that run 60 watts of power. If we are out on a search we will station one member on top of a mountain to relay communications from one search vehicle to another because, to repeat, if two of the vehicles are separated by a ridge or hill or mountain they will not be able to communicate directly. The Sheriff's Office and EMS have repeater stations on mountaintops all over the county - that is how they manage to communicate in mountainous terrain.

 

[bmaverick]

GMRS is on FM. To see how well FM stations are in your area getting around hills and into shallow valleys, I first use this tool.

Radio-Locator.com

Stations with higher power tend to have a better contour pattern. They may not reach to the bottom of a hill, yet are effective at the mid-point to the top of a hill.

AM is Amplitude Modulation, brings in too much white noise unless there is enough power behind it to drowned the noise out. AM is weak to penetrate building walls. Much of the time you need to bring the radio near a window or upstairs. AM has one advantage over FM, it can travel as ground waves.

FM is Frequency Modulation, used for shorter distances with little white noise. Using enough power will allow FM to penetrate building walls.

The range of FM transmission is related to the transmitter's RF (output) power, the antenna gain, and antenna height.

Now we can talk all about radio coverage, line-of-sight comms, but the future will all go to Starlink phones. The line-of-sight is straight up. With so many of them, they will act as data repeaters and communication repeaters globally and locally.

Starlink is now approved by the FCC with T-Mobile into the LTE cell phone system.

https://www.t-mobile.com/coverage/satellite-phone-service