These small hand-held units are commonly promoted as having up to a 5 mile range, and sometimes claiming as far as 7 miles.

What type of realistic range in normal conditions can you expect? And how can you maximize this range as much as possible?

Getting the Best Range from your CB, FRS, GMRS or MURS walkie-talkie
	Perhaps the most surprising discovery - both in theory and in testing - is that the power of the transmitting radio has very little impact on its effective range. A radio that is four times more powerful than another one may in fact offer no greater working range! Part 2 of a 5 part series - click for Parts  One  Two  Three  Four  Five

FRS radios are advertised as having a range of 'up to two miles'. I have typically experienced 0.25 - 0.5 miles. Disappointing, but usable.

And then I read an advertisement for an 'up to seven miles' GMRS radio. Wow. It had four times the power of the FRS radio, was newer technology, and seemed very promising.

Care to guess what its actual tested range was? Hint : Very much less. But manufacturers can promote these almost impossible range claims due to the complexity of what determines the working range of a radio.

Oh - the actual range I get from these radios? I'll tell you in part three.

Marketing Hype vs Actual Reality

Perhaps conveniently for sellers of two-way radios, the actual effective range between two radios can vary enormously depending on many different factors.

A cynic might think this is why radios that give less than one mile of range are promoted as having ranges ten or twenty times further!

Most of the factors influencing range are out of our control, but there are several factors that we can sometimes optimize. Here is a list of the major issues that relate to effective radio range.

You'll get more range if you get higher.  Even something simple like holding the radio above your head (and using an extension microphone) can make an appreciable difference in range.

Topography

In some respects, radio waves are similar to light from a light bulb (indeed, light is just a higher frequency form of radiation that is otherwise essentially identical to radio waves).

And so, with this in mind, here's a quick rule of thumb. If you can see the person you're trying to communicate with, you are probably within radio range, no matter which type of radio you're using.

The idea situation would be if the two of you were on boats on a smooth sea, with nothing else between you. This would give you the best possible range, and is probably the type of scenario that manufacturers have in mind when they make their outrageous claims.

Obstructions

If there are things between you and the other person, then, depending on the nature of these obstructions, your ability to send a radio signal between you will be reduced and perhaps eliminated.

Radio waves do not pass very well through conductive metal. They don't much like high density materials (eg concrete) either.

Sometimes all it takes is to move a few inches to change from a dead spot to a spot where you have a clear signal. You might notice this with your car radio - when tuned to a medium-weak signal, and while stopped in a line of traffic, you'll often notice that just by moving a few feet you can change from a bad signal to a good signal.

Radio waves don't like traveling through the ground or water either. This means if you and your friend are on opposite sides of a mountain, or if one of you is in a tunnel, you're unlikely to be able to communicate.

Note that in some tunnels, you might have cell phone and even FM/AM radio reception, but this is because the tunnel has built in 'repeaters' that pipe the radio signals from outside the tunnel and then rebroadcast them inside the tunnel.

Biggest Obstruction of All - You

People absorb radio waves. This is the same concept that a microwave oven uses, but whereas a microwave oven is focusing 1000 watts of energy into one or two pounds of food, you are only absorbing a small percentage of one or two watts, and you weigh perhaps 150-200 lbs.

Yes, that does mean that you are being slowly cooked. But the watts of power per pound of flesh is very much lower than in a microwave - perhaps 100,000 times less, and so most people believe radio radiation to be relatively harmless. However, increasingly convincing studies are suggesting that even low powered radios and cell phones, if used for long periods of time and held close to you, may cause cancers or other problems.

Which means there are two reasons to avoid absorbing any more radio waves than you have to. The first reason is for your health!

The second reason is because, obviously, the more radio power you absorb, the less that can be transmitted or received - the shorter the range your radio will have.

Two simple things will minimize the power you are absorbing. First, don't hold the radio anywhere near its antenna. Secondly, don't have the radio clipped to your belt - instead, hold it away from you (consider using an extension microphone for best results). These two things can make a big difference - in the worst case scenario, you might be inadvertently absorbing as much as 80% of the radio energy being radiated; in a best case scenario, you'll perhaps be absorbing 10%-20%.

Another Big Obstruction - Your Car

If you are using a radio inside a car, then the metal frame of the car shields a lot of the radio signals from getting in from outside, and shields even more of the signals you transmit from inside getting out again.

To get the best range in a car, hold your radio with the antenna as close to a window as possible so that it can 'see' out in as broad an area as possible.

Earth's Curvature

In theory, like a beam of light, radio waves travel in a straight line. But, in practice, lower frequency radio waves (like AM radio) actually curve around the surface of the earth, which is why AM radio signals can travel very much further than line of sight. CB radio signals are almost too high a frequency to curve, but they do have a little bit of curvature present. Other (higher frequency) radio signals go in straight lines only.

There is another interesting exception to the 'beam of light' principle. Some radio waves reflect off the atmosphere and then 'bounce' back down to the earth. The extent of the bounce can vary depending on the time of day and the level of solar activity from the sun.

CB frequencies usually just go through the atmosphere, but occasionally they will bounce back. The strange result of this is that you might find that a person 30 miles away is out of range (beyond regular range), but a person 100 (or even 1000+) miles away is clearly in range, due to a signal bouncing up and back down again.

This 'DX' or 'skip' feature of CB radios is usually a nuisance rather than a help, because all of a sudden, your channel might become crowded with unwanted extra signals from hundreds or thousands of miles away, making it difficult to communicate with your friends on the next block.

Interference

If there are other people transmitting on the same frequency, or sometimes on an adjacent frequency, then the worst case scenario is that you can't use that frequency at all - their signal blocks out your signal.

When two people transmit on the same AM frequency, the two signals interfere with each other and usually all you hear is a high pitched squeal.

When two people transmit on the same FM frequency, the stronger signal typically completely obliterates the weaker signal.

It makes no difference who started transmitting first. The laws of radio physics basically say that two people can't use the same frequency at the same time. Any time that you see what seems to be two people using the same frequency at the same time (for example on a cell phone when you can talk and listen simultaneously) what is happening is that the cell phone is actually using two different frequencies - a send frequency and a receive frequency. And the person next to you - also using a cell phone - he is using another two more frequencies.

Sometimes a person is transmitting a very powerful signal on one frequency that is so strong that it overwhelms your receiver, and some of its transmission frequency 'spills over' into your receiving frequency as well. This can be a problem with poorly tuned equipment (or too powerful), and the only thing you can do is try and move to another frequency further away from the interfering channel.

In addition to this obvious interference, weak interference - from other people transmitting a long way away - can also interfere with the clarity of your signal, particularly as the range between your own radios increases.

If you're hearing background interference becoming stronger on the channel you are using, simply switch to a different channel that might be less busy.

Squelch

The chances are that your radio has an automatic squelch function. This is not as good as a manual squelch.

Squelch cuts out the background noise that you would otherwise hear when there is no-one transmitting on the radio. If you tune your AM radio to a space between stations, you'll hear some 'static' or background noise. A squelch control tells the radio 'ignore anything that is just a weak background noise or meaningless static and don't play those sounds through the speaker at all'.

This is great when it correctly guesses what is unwanted meaningless static (to ignore) and what is an important but very weak radio broadcast (to play through the speaker). With a manual squelch control, you can carefully balance this setting, but with an automatic one, you will find that it is causing you to miss weak broadcasts.

Manual squelch controls require more work on your part, but, if adjusted correctly, will give you more range than an automatic squelch control.

Receiver Sensitivity

Not all receivers are equally sensitive to weak signals. The more sensitive a receiver is, the better a job it will do of pulling in the weak signals and making sense of them, presenting them to you as something you can clearly hear and understand.

Choosing a radio with excellent receiver sensitivity (and selectivity) is more important than choosing one with high transmission power.  You'll get longer battery life with a lower powered but more highly sensitive radio, and usually get better range, too.  This is illustrated dramatically in part four of this series.

Receiver sensitivity is usually measured, in a radio's specifications, in terms of microvolts for so many dB of either signal/noise ratio (CB and AM radios) or SINAD (FM radios such as MURS, FRS and GMRS). The lower the number, the better.

Note that some radios don't disclose their receiver sensitivity. It is a safe bet, in such cases, that the receiver is not a very good one!

For a CB radio, you would expect to see sensitivities no greater than 1.5 uV for 10dB of S/N. A good receiver would have a sensitivity of less than 1.0 uV and a great receiver would have a sensitivity of less than 0.7 uV.

For MURS, FRS and GMRS, you would expect to see sensitivities no greater than 0.5 uV for 12 dB SINAD. A good receiver would have a sensitivity of less than 0.3 uV and a great receiver would have a sensitivity of 0.2 uV.

Transmitter Power

The answer to this issue surprises many people. For CB radios, more power usually gives you an appreciable impact in terms of more range. But, for the higher frequency radios, an increase in power has little or no impact whatsoever.

The reason for this is two fold. Firstly, the maximum range of these radios is 'line of sight'. To achieve this range, the radios do not need very much power. More power will never get the radios to transmit further than 'line of sight' and if moderate power (0.5 - 1 Watt) is enough to achieve the maximum line of site range, any more power is unnecessary.

The second reason is that, depending on the type of antenna you are using, range is proportional to somewhere between the square root and the cube root of the power. In other words, if you double your transmitting power, the best case scenario is that your range will only increase 40%, and the worst case scenario is that it will increase less than 25%. Increase power ten fold, and range may not even double.

The third reason is that many of the factors preventing radios from achieving their maximum 'line of site' range are so major that even a ten fold or twenty fold increase in the radio's transmitting power might not have much impact. If much or all of the transmitting power is being soaked up by a building or a hill (or by you!) then increasing power will not solve that problem, it will merely feed even more power into the building or hill or person.

In our testing (described in parts three and four) we found that the design and quality of the unit was more important than its power. You'll get better results with a high quality low power unit than you will with a low quality high power unit. And your batteries will last longer, too!

We did testing using two identical dual power units (Motorola G223 GMRS radios) and compared their range when using low power (0.5 watt) and high power (2 watts). There was almost no difference in range whatsoever - perhaps the higher power would sometimes provide an extra 1/10th of a mile in range. Interestingly, these radios were regularly out-performed by a low power 0.5 watt pair of FRS radios, which confirms that receiver sensitivity and overall design are more important than power by themselves!

Batteries and Voltage

The power that the unit is capable of transmitting is a function of the square of the battery voltage. Voltage is very important. If you are choosing between regular alkaline batteries (at 1.5 volts each) and Ni-Cad or NiMH batteries (at 1.2 volts each) you will get a 56% increase in transmitted power with the alkaline batteries.

Sure, more power doesn't always mean more range, but that is no reason to accept any less than the most power your unit is capable of generating. Keep your batteries fresh and fully charged.

Antenna

The FCC limit a FRS radio to only using its fixed small antenna built into the radio unit. But the other three types of units are allowed to have external antennas.

Some models of GMRS and MURS radios are designed for external antennas, while others do not. Almost all CB radios are designed to allow for an external antenna.

You will get noticeably better results and more range with an external antenna. Indeed, you'll usually find that the single most important thing you can do to improve your effective range for both transmitting and receiving signals is to get a properly designed and properly tuned antenna for your radio, and to locate it in the best position possible.

Of course if you're using a radio as a portable unit while walking around, there isn't much you can do about getting a better antenna, although sometimes you can substitute the standard short (eg 3") antenna for a longer (eg 6") antenna and that might give you some effective extra range.

The best opportunities for an external antenna are if you are using the radio in a car or in a fixed location (home or office). You can then locate an antenna outside of the car (remember that the car shell stops a lot of the radio waves from traveling in or out of the car) or house/office (radio waves don't much like concrete, either!).

An antenna can also be mounted higher up, so as to be clear of more obstacles and to have better line-of-site to the other unit you are communicating with.

There are three more benefits of an external antenna. First of all, it can sometimes give you a 'ground' as well as an antenna (half of your radio signal needs to go to a 'ground' - if you don't have one, then that half is being effectively wasted).

Secondly, the external antenna can be made the exact length to work best with the frequency of your radio. Every radio frequency has a matching wavelength size, and an antenna needs to be an exact percentage of this size for maximum efficiency (usually about half the wave length is ideal).

Thirdly, an external antenna can be designed to concentrate the radio signal in certain directions. Instead of allowing the signal to radiate in every direction equally like a sphere, a good antenna will typically make it radiate out in a flat circle. There is no need to send signals straight up or straight down - the people you are wanting to talk to are usually at the same level as you, just at a distance away. By directing the signal only into the horizontal, none of the signal is wasted, and you end up getting as much as double the range as you would with a plain undirected antenna.

If you are planning on using radios in cars, then you should get an external antenna. An external antenna for a GMRS radio is a very small short thing - it can be as little as six inches in height, and will probably have a magnetic mount to simply stick to the roof of your car. Its wire can be fed through the rubber around the car door jamb.

A CB radio antenna is much larger - perhaps as much as 3 ft in length or more.

If you do get an external antenna, you should use a SWR meter to complete the fine tuning of the antenna, to ensure that it is best balanced and matched to your transmitter. Most antennas are 'tunable' (usually by slightly varying their length) and the difference between a properly tuned and a badly tuned aerial can be as much as 50% in terms of effective power lost.

Summary - How to Get the Best Range

More power is good, but not the most important thing.

The biggest impact on range will be the actual design of the radio - its receiver sensitivity in particular, and how viciously its squelch cuts out weak signals. Get a unit with manual squelch, if possible, and with a very low number for its receiver sensitivity.

The other most important impact has to do with your antenna. If it is possible to have an external antenna (FRS radios are not allowed external antennas, the other three types are) then this will make a positive difference. If you are stuck with the built in antenna, try and hold the radio as far away from you as possible (ie up in the air above your head - use an external microphone) and, if in a vehicle or building, as close to a window as possible where it can 'see' in the direction of the person you're hoping to communicate with.

Rechargeable batteries are wonderfully convenient, but if your radio is designed for using the same number of either regular alkaline or rechargeable batteries, you'll get more range from the higher voltage alkaline batteries.

See also Parts 1, 3 4 & 5

In Part 1 we explain the different types of personal radio services available to you, and what they variously mean.

In Part 3 we give you real world test results and help you choose which is the best system for your needs.

In Part 4 we repeat the testing, this time using 'professional grade' radios to determine just how much more performance you get from these much more expensive radios.

In Part 5 we explain the confusing mismatch of channel number allocations to different FRS/GMRS radios.

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Originally published 18 July 2003, last update 20 Jul 2020

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me (David Rowell - KF7VVM) as original writer.