Overland Tech: Trail Comms

Overland Tech: Trail Comms

by Patrick Rich

Whether you travel alone or in a group, having reliable communications is essential. Personally, a radio is where a lot of the trip’s moments are shared in my travel group and more than once I’ve needed a radio to find people or get vital trip information. It used to be the choice was pretty basic - CB or, well it was pretty much CB. Amateur radio, or ham - not an acronym - also existed but wasn’t really practical or desirable for most people until more recently. While that has changed somewhat, and while CB is still king of the hill for cheap and easy trail comms there have been some big changes in overland communication and new technologies that are worth discussing.  

This might be a little long, so I’ve broken it up into chapters, feel free to skip around.

  • Radio basics
  • CB pros and cons
  • Ham pros and cons
  • GMRS pros and cons
  • Which is right for you?

Radio Basics


While it might be a little elemental, I think it’s important to start with a few radio basics that help frame the rest of the discussion. If you’ve heard this all before, feel free to skip ahead. 

A radio works, in its simplest form, by taking an input signal, amplifying it and sending electromagnetic energy into an antenna to produce a radio wave which radiates out into space.  

The wavelength of the signal is the distance from the peak of one wave to another. For amateur radio, regions or bands of the radio spectrum are referred to this way, but for most applications frequency is used. Frequency measures the waves per second and is given in Hertz (Hz.) 

A carrier wave can be manipulated in a few ways, by modifying the amplitude of the wave (AM) or by modifying the frequency of the wave (FM). You can also use only half the wave at double the power (SSB) or pack the FM signal with more information using digital modulation. Regardless of the technology, from CB to cell signal or even GPS, the principles are the same - waves sent, waves received.  

Something else generally the same with all radio transmissions is their physical limits for travel. Waves travel perpendicular to the antenna as they radiate outwards in 3 dimensions and don’t curve with the earth. What this means is that radio is generally line-of-sight and is limited by how far away the horizon is from you. More specifically, the limit is the radio horizon which is the distance the top of one antenna could physically see the top of the other. Given the curve of the earth and the height of most users this is a little over 3 miles on completely flat terrain. No matter what the marketing says, range is mostly limited by this physical limitation not by power or technology.

The frequencies for radio are part of the larger electromagnetic spectrum. The RF spectrum is a limited resource - we can’t create more and there are many users vying for space. Like all limited resources, the RF spectrum is tightly regulated to prevent abuse and interference that could range from annoying to deadly. As a recent example, the FAA recently released an airworthiness directive, warning about certain 5G signals interfering with airplane and helicopter radio altimeters. In this case certain signals can make altimeters read unreliably and could be dangerous during instrument approaches and landings, severely limiting when some airlines can actually land at some airports. It can be a big deal. In the US, the FCC is the agency that controls the spectrum.


So armed with information about radio spectrum, wave propagation and modes we can talk about radio options for the overlander.

CB


History

Citizens Band was the FCC’s first real effort to carve out spectrum for the general population to use and has been in use for over 70 years. It was meant for person to person communication, but also for radio control hobbies. 

Technology

CB is 27 MHz or roughly 11 meters. The signal is AM. The long wave is good for terrain and under the right conditions can travel very long distances. This band is considered High Frequency (HF) which means that in some atmosphere conditions a CB signal can be heard FAR beyond the radio horizon. The AM signal combined with this long wave unfortunately means that clarity of signal is poor and it also means that the antenna needs to be physically large. The power you can transmit on CB is low at 4 watts for full wave (common), or 12 watts for SSB (far less common).

Benefits

The standard CB radio is very cheap, easy to use, requires no license and it’s very common in off-road groups. You can even find CB radios, antennas and parts in almost any truck stop today making parts and service very easy to find. CB is a good cheap way to equip a group with convoy communications within line of sight. I’ve been using one for 6 years and despite its limitations, it has worked well for my convoy communications in that time.

Downsides

CB feel every bit as old and outdated as its reputation.

Pros: Cheap, easy, ubiquitous.

Cons: Poor clarity, poor range.

Verdict: An easy way to get into basic convoy communications.

Ham


History

The history of amateur radio is basically the history of radio itself. However, it’s only been in the last 40 years or so since the transistor and eventually the IC, that off-road amateur radio has become practical for every day use by regular folks. 

Technology

Amateur radio encompasses a large portion of the RF spectrum with various privileges granted based on licensing tiers. With a license and callsign you are, in the eyes of the FCC, a radio station. The 1st level of licensed amateur is “technician” which grants the user access to frequencies as low as 3.525 MHz or as high as 1.3 GHz. For overlanding, 2 meter VHF (144-148 MHz) and 70 centimeter UHF (420 - 450 MHz) are the most commonly used. There are many modes of transmission available including AM, Single Side Band (SSB), FM, digital, etc. Technicians are allowed to transmit at up to 1.5KW of power, though even the most powerful mobile transmitters rarely exceed 100 watts. In addition to voice, amateur radio can act as a modem to transmit digital data of any type, usually in small bursts or packets. The power of amateur radio for the overlander is the scope of options.

Benefits 

The biggest feature that you get with amateur over something like CB is access to repeaters. We know that a radio signal is basically limited by the horizon, so how do you get around this limitation? We’ve known for some time how to bend the signal:

  • Relay the signal
  • Put the signal up higher


A repeater takes in a signal on one frequency and retransmits it on another that can be received by a radio tuned to the right set of frequencies. By putting this repeater up high a signal can travel much further than it could possibly do otherwise. A repeater with even a mild elevation gain of, say, 25 feet takes the horizon between 2 radios from 3 miles to 20 miles (10 miles to the repeater from one handheld, 10 miles from the repeater to another handheld). Put that repeater up on a mountain top 5000 feet above the valley floor, and you have a communication range of over 200 miles, even with a small handheld radio. Also, repeaters can even be linked together so that a signal can relay through many stations, making communication range virtually unlimited.

Because amateur radio has been around for a long time, and because 2M and 70CM are popular bands, there is an abundance of free, publicly available repeaters in a given area. Even in very remote areas the chances of being able to access a repeater are fair to good. If you know the frequencies and tones you can access these repeaters as needed and increase your communication range dramatically.

Amateur radio isn’t limited to voice. A common, free, widely available service called APRS (Automatic Packet Reporting System) is often very helpful for the overlander. You can report your position, locate other stations, get weather reports, and even send and receive texts from mobile numbers using small packets of data that get relayed along until they find a internet gate. It’s even possible to connect to the internet through a kind of special amateur radio VOIP that allows you to talk to people worldwide if you desire, or hey... why not talk to the international space station?    

As I said, vast.  

Downsides

To start, you are required to take a test ($15) which gets you a callsign and a license for 10 years (which is easily renewed). The test isn’t merely a formality and will require some study time for most. There are also no “channels'' to make it a simple plug and play operation. With amateur radio you will have to know what you are doing with frequencies, tones, modes, offsets, etc. for it to be legal and to work at all. The radio spectrum within the bands is fairly tightly controlled by volunteer coordinators and you can’t just punch in a frequency and hope for the best either. 

This is relatively easy to mitigate however, as even the cheapest ham radios are programable to store commonly used frequencies and settings and you can usually download a list of stations for free using software. On the topic of cheap, there are many very low cost ways to get equipment, as low as $25 or so making it even cheaper than CB. It’s also not hard to spend a lot if you want a feature-rich experience. While amateur radio isn’t easy, it is powerful and flexible and a valuable tool for the overlander willing to invest the time.

Pros: Extremely powerful and flexible, access to a large network of repeaters, affordable, feature rich.

Cons: Not user friendly, requires license test, may be overkill for many users.

Verdict: Nerdy, complicated, powerful.

GMRS


History

If you’ve read this far and thought “isn’t there a way to get the benefits of ham with the ease of CB?” you owe it to yourself to keep reading. 

In the 90’s the FCC created a more user-friendly CB type service but built on more modern technology. The FRS (Family Radio Service) allowed people to go out and buy relatively affordable and easy to use handheld radios and immediately get on the air. GMRS (General Mobile Radio Service) is a more powerful version of the FRS idea, that blends a little amateur radio and a little FRS.

Technology

GMRS and FRS use the 65 cm UHF band from 462.5625 MHz to 467.7250 MHz. The combination of shortwave and FM combination gives excellent audio quality. GMRS and FRS share 22 channels but have very different users and very different requirements. FRS, limited to either .5 or 2 watts maximum power and fixed antenna is meant for family communication at short ranges. GMRS is allowed up to 50 watts of power and does allow for removable antennas, though most handheld radios have fixed antennas and 5 watts power. The increased power output and the ability to use remotely mounted high gain antennas significantly increases range over FRS. Both FRS and GMRS also make use of “privacy channels” or PL tones.

A common misunderstanding is that these privacy channels are discrete sub channels. Tones are in fact only ways to filter out, or squelch, signals that aren’t preceded by an audible tone, either using the CTCSS or DCS method. Notes: Anything said on air using either FRS or GMRS is public and can be heard by anyone listening in, FYI, regardless of tone settings. These tones also serve another function, which is access to open the repeaters.

Because GMRS is more powerful, a license is required by law to operate on it. You don’t need to take a test and a $70 fee covers an entire family for 10 years. When you get a license you get a call sign that you are required to use to identify your station when using GMRS (anything above 2 watts power on any of the 22 channels).

Benefits

FRS is easy, cheap and clear but it’s limited to handhelds with small antennas and limited power. GMRS is everything FRS is and more: more power and remote antennas allow for much further range and flexibility. GMRS and FRS radios are easy to buy anywhere and a lot of people have them already, making compatibility high. GMRS radios are also not limited to handheld units, which require batteries and can be cumbersome to use while driving, and base units are available.

Repeaters are a big reason that amateur radio has been so popular for the overlander. With GMRS, there are 8 repeater channels if your radio has the ability to access them. 

Recent changes in the law have given GMRS one of amateur radios best features - digital packet transmission. Allowing for transmission of position, or other data much like APRS. As of this writing, however, there are no radios which take advantage of this and no network to support it. It may come in time or it may be limited to a simplex/radio to radio feature within a certain brand or model.

Downsides

The main downside of GMRS is that repeaters are relatively new, expensive and completely volunteer, which makes them rare. Even more rare are “open” repeaters that anyone has access to without belonging to a club or requesting access ahead of time. There aren’t a ton of people making base units right now so choices are slim, but good. Honestly, one of the biggest drawbacks of GMRS is its popularity.  Because the channels are shared with FRS radios, which have been sold for 30 years and because the radios are so common now, you will find that there is a lot of cross traffic on GMRS/FRS anywhere within a few miles of people, and especially anywhere popular.  

Pros: High power, flexible antenna mounting, access to repeaters, easy to use, compatibility with radios many people already have, no licensing test.

Cons: Paid license required, limited repeater network, handheld radios are cheap but mobile units can be expensive.

Verdict: Easier than ham with many of the benefits for the overlander.

NOTE: In Canada, handheld GMRS units with less than 2 watts of power are legal, but base units, removable antennas, power greater than 50 watts or duplex communication (repeaters) are not currently legal.  

Which radio is right for you?

If you like to tinker, then ham certainly offers the most room to grow. On the other hand GMRS offers most of the benefits of ham without the steep learning curve. As far as CB? Well, honestly, it’s still the system that is in use by most groups and some groups still require it for trail comms. Of course, you can do like I do and just have all 3. Seriously though, probably don’t do that. Let’s break it down

CB - Short range and poor voice quality, but very cheap and very common.

GMRS - Popular, perhaps too popular but lots of power, quality of voice, repeater access and future features.

Ham - Lots to know, but all the options.

With everything that's been said, the system you go with will honestly be decided mostly by who you are trying to talk to. The best technology won't mean anything after if there isn't anyone listening. If you are traveling solo cross country, then ham might be a worthwhile investment. If you are often out in large 4x4 groups, a CB may be a requirement. I have all three and the one I use most is actually my CB because it's what everyone has. If I were to rewind the clock I would probably go GMRS first, then ham, and skip CB.

It's also worth noting that this guide is for primarily the United States and while the principles discussed are valid everywhere, frequency allocation, programs and regulation will vary. 
 

 

Lastly, I leave you my impassioned plea to keep it legal. It's stupid easy to get transceivers that will allow you to transmit on frequencies you don't have permission to use, both for ham and especially for GMRS. I have several of these radios myself, and used properly they are a serious value, and completely legal*, but can easily be abused. Don't be that guy that does just because they can. 

*In Canada it is illegal to program one of these radios for use on FSR/RR frequencies.


1 Response

Kent Ratke
Kent Ratke

January 05, 2022

Awesome summary, honestly not a topic covered nearly enough on the internet. Great layout, breakdown and info.

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