GMRS Radio Basics: Overlanding, Off-Roading, and Backcountry Adventure
For years, I had a trusty old CB radio mounted on the dash of my Jeep so that I could communicate with my buddies when we were on the trail. I have a lot of nostalgia for my CB, but times change. There’s new tech in town.
Enter General Mobile Radio Service (GMRS), a more modern radio communications technology that is taking over the off-roading and overlanding world. After realizing that many of the people I met on the trail were switching to GMRS, I myself have recently bid my CB adieu.
In this article, I’ll share what I’ve learned about GMRS radios and why they’re quickly becoming the go-to choice for off-roading and overlanding. I’ll also go over some of the basics of using them to help you get up and running quickly.
If you are looking for recommendations on specific models, check out our article on the best handheld GMRS radios. I’m planning to put a similar one together on mobile GMRS models soon.
Before we move on though, it’s important to note that you must acquire a license from the FCC to use GMRS radios. The permit cost $35 at the time I am writing this and doesn’t require a test. The FCC classifies any radio operating on FRS/GMRS frequencies with more than 2 watts as a GMRS radio. You can obtain the license here.
What is GMRS radio?
Put simply, GMRS radios are two-way radios that allow users to communicate with one another. They have become increasingly popular in backcountry use, including overlanding and off-roading, where they are most often used to communicate among vehicles.
There are two types of GMRS radios: handheld and mobile. I know, the terminology is already a bit confusing. Aren’t handheld radios mobile? Bear with me.
The industry uses the word “mobile GMRS” as shorthand to refer to larger, more powerful units that are installed in a vehicle and typically rely on the vehicle’s battery to provide power.
Don’t quote me on this, but I suspect this use of mobile for GMRS units stems from “mobile ham radio,” the term used in the amateur radio community to reference ham radios used in vehicles (as opposed to stationary units in homes).
The handhelds look like your classic walkie talkie, have an integrated battery, and are less powerful (had thus have less range) than the mobile units. One of the reasons GMRS has gotten so popular is the availability of these two types of radios, but more on that later.
Taking a step back, GMRS is one of several radio technologies that operate on frequency bands that the government has set aside for civilian use. Others in the category include Amateur Radio (ham), Citizens Band (CB), Family Radio Service (FRS), and Multi-Use Radio Service (MURS), which I covered in a previous article on overlanding communications. The Federal Communications Commission refers to these types of radios collectively as “personal radio services.”
As a side note, that article covers concepts and terminology of two-way radio comms that might be helpful if you are just getting started.
GMRS operates on 30 channels in the ultra high frequency (UHF) range around 462 MHz and 467 MHz. I’ll include more detail on these frequency bands below, but for now I’ll just say that GMRS overlaps with FRS radios on 22 bands, which comes in hand out on the trail.
Why has GMRS become so popular?
To understand why GMRS has been so rapidly adopted for off-road, overlanding and other backcountry pursuits, it helps to compare it to the other technologies that preceded it.
One frustration that I ran into was that I could only use my Jeep’s CB radio to talk with other people who have CB radios. At any given trailhead some people will have CBs, others FRS radios, and some industrious types will be running ham radios.
GMRS radios operate on both GMRS and FRS frequencies, so mobile and handheld GMRS units can communicate with each other and with FRS radios.
Handheld GMRS and FRS units are cheap and relatively easy to use (no complicated vehicle install or test to study for and pass, as with ham radio). Nowadays, people who have CBs and ham radios in their rigs often also have a GMRS or FRS handheld so they can communicate with the group.
This low barrier to entry is a major reason that many off-roading clubs have adopted GMRS as the club radio technology. Ham radios, which offer vastly greater range than other technologies, require studying for a test, which prevents a lot of people from getting their license.
A GMRS license, in contrast, is easy to purchase from the FCC and requires no test. There’s a bit of a network effect going on, where the more people who adopt GMRS, the more it makes sense to get one.
Better Range and Signal Quality
The primary competitor for GMRS for off-roading and overlanding has long been CB radio. While in theory, CB radio could have a longer range than GMRS due to its radio frequency, in practice, GMRS radios often perform better. There are several reasons for this.
While the power output of different mobile GMRS units varies, the maximum power output can range up to 50 watts under FCC guidelines. In contrast, CB radios are limited to a maximum power output of 4 watts, which limits their range.
Handheld GMRS units typically operate at a maximum of 5 watts, which is double the power of FRS units, the other primary style of walkie talkie used for overlanding and off-roading. They can also operated on 0.5 watt channels (see below).
Another advantage of GMRS is that, unlike CB signals, GMRS signals are less impacted by the solar cycle, which peaks every 11 years or so and affects the “weather” on the sun’s surface. This solar activity can cause significant noise and interference, making it difficult to communicate with units only a mile away.
GMRS radios get another boost in range through the ability to use signal repeaters. These are devices that receive and amplify weak radio signals and then re-transmit them to a larger area, increasing the range of two-way radio communication. GMRS repeaters typically have a broadcast range of around 25 miles. So if you can hit a repeater, you can reach other GMRS users within that distance.
Because GMRS radios are digital technology, they can utilize signal repeaters to extend their range and improve the clarity of radio communication. CB radios are analog technology and cannot use signal repeaters. Ham radio can use repeaters, but the lack of adoption of the technology has it ham-strung. Hehe.
The last thing I’ll mention in this section is that the UHF radio waves GMRS units produce can easily travel through small spaces, so the radios may work better than CBs in forested areas. For a detailed explanation, check out our guide to using GMRS repeaters.
More Channels and Privacy
One of the downsides to CB and FRS radios is that the channels can often be crowded. The chatter can make it difficult to communicate with your group and the competing signals can cause interference, degrading the signal. This is another area where it’s GMRS for the win.
GMRS radios offer more channels than CBs, providing users with more options for finding a clear channel to use. Also, GMRS radios offer the ability to use privacy codes, also known as sub-audible tone codes or privacy tones.
These codes reduce interference from other GMRS users on the same channel by adding a tone to the radio signal that is inaudible to the human ear, but can be detected by the receiving radio.
FRS radios can also use privacy codes, but CBs cannot, as an analog technology. Using a shared privacy code, you can ensure that only your team’s radios receive your transmissions, increasing privacy and reducing the chances of interference. Here’s a video that explains privacy codes:
How to get started with GMRS
Now that I’ve convinced you that GMRS is the way to go – maybe? – I’m going to give you a quick step by step on how to get started.
Getting started with GMRS radio is pretty straightforward, and it all starts with deciding what kind of GMRS radio you want. The two main options are handheld and mobile GMRS radios.
While you may want to get both eventually, I recommend getting a couple of handheld GMRS radios first. They are versatile and may be all you will ever need.
To find a quality handheld radio, you can do research online, ask friends who use GMRS radio or check with your local off-road club for recommendations. For guidance on picking quality handhelds, check out this article.
Get a License
Anyone operating a GMRS radio must obtain a license from the FCC. I’ve read that the license cost around $70, but at the time I’m writing this it cost $35–not sure why the change or whether it will stick. No test is required – although navigating the FCC’s very confusing website can be a test of patience…
The FCC classifies any radio operating on FRS/GMRS frequencies with more than 2 watts as a GMRS radio. You can obtain the license here, which covers you and your family members for 10 years. Your drinking buddies don’t count as family, at least in the FCC’s eyes.
After you are approved for the license, the FCC will issue a Federal Registration Number (FRN), and is a unique identifier assigned to entities (individuals, businesses, etc.) that hold licenses for GMRS use. You can use this number to look up information about your license on the FCC’s Universal Licensing System, where you can find your call sign (the sequence of numbers you will use to identify yourself while transmitting (see below).
Understand the Basic Rules and Etiquette
Once you have your radios and your license, you can follow the radio’s instruction booklet to get up and running. I recommend listening in on public repeater frequency for a bit to understand how other users operate. The website myGMRS.com has a directory of repeaters around the country and you can most likely find one near you.
The FCC has a few rules governing GMRS use which cover things like not whistling, playing music, or using obscenities and not broadcasting political propaganda. No one is actually out there policing the airwaves for these things, as far as I can tell, but the rules seem like common sense and following them insures you annoy other radio users. Basically, don’t be a jerk.
The FCC requires that you announce your call sign at the end of every transmission and every 15 minutes during a long transmission that’s longer than 15 minutes. When announcing your call sign, you can say something like: “This is WXB202.” It’s that simple.
What is the signal range of GMRS radios ?
Some questions in life have a simple answer. The question of how far a GMRS radio signal will transmit clearly is not one of them.
Due to the frequency range at which they operate, GMRS radios use “line of sight” transmission, meaning that the radio signals travel in a straight line for a certain distance. If the receiving and transmitting antennas are not in line of sight of each other, the signal will be weakened or lost completely, reducing the range of the GMRS radio.
In broad strokes, GMRS radios will transmit anywhere from half a mile to 30 miles depending on a number of factors. These factors include:
Factors Impacting Signal Range
- Antenna height: The higher the antenna, the greater the range as the signal has a clearer path to travel.
- Power output: The higher the power output, the greater the range of the radio.
- Terrain: Hills, mountains, and other obstructions can reduce the range of the radio, which is a common issue when traveling in the backcountry.
- Weather conditions: Rain, fog, and other weather conditions can affect the signal quality and reduce the range.
- Interference: Other electronic devices, such as other radios or cell phones, can cause interference and reduce the range.
- Frequency: The frequency of the radio signal can also impact the range.
So, the range of a GMRS radio can vary greatly depending on the environment and the specific conditions. Handheld GMRS radios operate at lower power than mobile units, and so have a shorter range.
In the backcountry, on open, level terrain, two handheld GMRS radios could be expected to have a range of 2-3 miles, while two mobile GMRS units might be able to communicate at 15-20 miles. In mountainous areas, you lose a signal on any GMRS unit as soon as they round a corner or drop out of sight over a hill.
What is the difference between GMRS channels and frequencies?
When you first take a GMRS unit out of the box and turn it on, you’ll probably be confronted with two different modes: channel mode and frequency mode. So what is the difference between channels and frequencies?
Most GMRS users will default to channel mode, in which the radio is pre-programmed with specific “channels” that correspond to certain frequencies. In some ways, it’s just a way of simplifying the names of frequencies so they can be identified more easily. It’s a lot easier to remember “Channel 16” than “462.5750 MHz,” the corresponding frequency. This mode is simpler to use, as the user does not need to know the exact frequency for communication.
In this mode, the user manually tunes the radio to a specific frequency. However, it requires a higher level of knowledge of radio frequencies and may require the user to program the frequency manually. Frequency mode is more flexible and is used by those who need to communicate on specific frequencies or in more advanced settings.
Below is a chart that shows the various channels and their corresponding frequencies. It shows what channels are shared by FRS and GMRS, and the maximum transmission power allowed at each of those frequencies. You might notice that the last eight channels in the table have an “R” after the number. These are channels used by GMRS repeaters.
Which is the best GMRS channel?
If you looked at the table above carefully, you might have noticed that the primarily qualitative difference between the GMRS channels is the limits on how much power can be used to transmit the signal.
The channels (and corresponding frequencies) break down into three groups:
Channel 8-14: Low Power = Short Range
Channels 8 through 14 allow a maximum transmission power of .5 watts, and thus have the shortest range.
Channel 1-7: Medium Power = Mid-Range
Channels 1 through 7 allow a maximum transmission power of 5 watts, and thus are best for medium range communications.
Channel 15-22: High Power = Long Range
Channels 15 through 22 allow a maximum transmission power of 50 watts, and will transmit the furthest.
So what’s the best channel to use? The one that matches your needs. If you’ll mostly be communicating within a short distance, use one of the low power channels. Handheld GMRS units will typically switch between
If you need to reach someone 10 miles away, use one of the 50 watt channels.
Also, remember that you can always adjust the power you use for a given channel. It’s courteous to use the least power you need to make a clear connection. So even if you are operating on a 50 watts channel, you may not need all of that to reach your friend who’s 50 yards down the trail. Turn down the power to use what you need.
What is the difference between repeater channels and simplex channels?
I mentioned before that GMRS radios can use repeaters, which can boost their signal. The channel chart above showed a list of “normal” channels, which are referred to as simplex channels, and repeater channels (which had the R next to them).
A repeater channel is a radio frequency that is used to receive and then retransmit radio signals to extend the range of communication. It is typically located on a tower or high location and requires a license to operate.
A GMRS simplex channel, on the other hand, is a direct radio-to-radio communication without the use of a repeater. It operates on a single frequency and communication can only occur in one direction at a time.
The details of repeater use are a bit beyond the scope of this guide. I’d recommend you practice in simplex mode first, before experimenting with repeaters. I’ll cover how to connect with repeaters in another topic.
That should cover the basics. A lot of the detail on using a specific GRMS radio will come from your user manual, but hopefully I’ve given you enough context here so that it all make sense.
If you haven’t read it already, I recommend checking out my general intro to overlanding communications. And for specific recommendations, my guide to handheld GMRS units. For more info on using repeaters, check out this article. If you have any questions, throw them in the comments below and I’ll do my best to answer them.
Over and out.