There are two main formats for two way radios. They are the ultra high frequency (UHF) radio and the very high frequency (VHF) radio. Neither frequency band is inherently better than the other. Each has its advantages and disadvantages. Both formats are effective ways to communicate with another person. But how do you decide which one suits your needs? Let’s go over the key components of both frequencies to help you decide.
Two-way radios communicate with each other through the use of radio waves. Radio waves have different frequencies, and by tuning a radio receiver to a specific frequency, it can pick up a specific signal.
Radio waves are transmitted as a series of cycles, one after another. You will always see the abbreviation “Hz” used to indicate the frequency of a radio. Hertz is equal to one cycle per second.
Radio waves are measured in kilohertz (kHz), which equals 1,000 cycles per second, or megahertz (MHz), which equals 1,000,000 cycles per second, or 1,000 kHz. The relationship between these units is as follows: 1,000,000 Hertz = 1000 kilohertz = 1 megahertz.
You may also hear the term “wavelength” when you hear about radio waves. This term is from the early days of radio when frequencies were measured in terms of the distance between the peaks of two consecutive cycles of a radio wave rather than the number of cycles per second. Lower frequencies produce a longer wavelength.
While wavelength measures the distance between the peaks of the cycles, frequency refers to the time measured between the “peak” and “trough” of a wave reaching the source. So frequency measures time rather than distance, but essentially they both say the same thing.
What is important about wavelength for two-way radios is that it affects the transmission range under certain conditions. A longer wavelength, as a general rule, allows a radio signal to travel a greater distance.
Lower frequencies or wavelengths have greater penetrating power. That is one of the reasons they are used to communicate with submarines. VLF radio waves (3-30 kHz) can penetrate seawater to a depth of approximately 20 meters. So a shallow submarine can use these frequencies.
So from what you read above, you may think that VHF is always the best option for a two-way radio, no matter where you are using it. That is not necessarily true. Although VHF has better penetration capabilities, that doesn’t necessarily make it the best choice for buildings. Remember the conversation about wavelength earlier? The wavelength has a great impact on transmission.
To explain this, suppose we are communicating from one side of a commercial building to the other. Between these two points is a metal wall with a three foot gate. Metal is an enemy of radio waves and they usually don’t get through.
For our example, let’s assume that the UHF wavelength the radio uses is about a foot and a half long and a similar VHF radio is about five feet long. These are in the ballpark of their normal wavelengths.
When the UHF transmits its signal, the one and a half foot long wave will go through the gate, since the gate is wider than the wavelength. The VHF signal will be fully reflected as it is wider than the gate opening.
Your microwave oven is an example of this. The glass entrance door has a metal mesh with very small holes. Microwaves, which have a very high frequency, have wavelengths only several inches long. The mesh keeps the microwaves trapped in the oven but allows you to see inside because the light waves have a microscopic wavelength.
Imagine walking through the building carrying a pole that is five feet wide. You will encounter the same challenges that a VHF signal faces. Now imagine walking through the building with a pole only a foot and a half wide as a UHF wave. There are far fewer doors you couldn’t go through.
The only difference is that wireless signals will penetrate through drywall, masonry, human bodies, furniture, wall paneling, and other solid objects. However, all of these objects will reduce the signal strength. The denser the object, the more it reduces the signal. VHF will get through these obstacles better than UHF, but that doesn’t necessarily mean VHF is better for indoor applications, as we’ll see in the UHF section below.
In our example above, we assumed you had a metal wall with an opening. If you reverse this and have a three foot metal object in front of the transmitting radio, then VHF would win. Since the object is three feet wide, it will totally block the UHF signal, while the VHF signal will go around it. Lower frequencies, like VHF, diffract around large smooth obstacles more easily, and also travel more easily through brick and stone.
For most applications, lower radio frequencies are better for longer range. A television broadcast station illustrates this. A typical VHF station operates at about 100,000 watts and has a coverage radius of about 60 miles. A UHF station with a coverage radius of 60 miles requires transmitting at 3,000,000 watts.
So there is no clear choice as to which is better, VHF or UHF. There is a lot of “black magic” in radio technology, so it’s not always easy to know which one will work best for your application. To help you decide which technology is best for you, more details on each are listed below.
UHF radio frequency
UHF equipment operates between the frequencies of 300 MHz and 3000 MHz. Until recently, it was not widely used. Now UHF radio frequency is used for GPS, Bluetooth, cordless phones and WiFi.
There are more channels available with UHF, so in more populated areas UHF is less likely to have interference from other systems. If you are in an area where the population is sparse, VHF should work just fine for you. Not too long ago, the FCC also opened up a new VHF frequency called MURS that is not widely used in most areas until now. There’s more on WALLS below in the VHF section. If you are in an area where interference from other radios may be a problem, UHF transmitters and receivers might be your best option unless you are using a MURS VHF radio. UHF is best for passing through physical barriers such as walls, buildings, and rugged landscapes. Anything that obstructs a radio wave will weaken the radio signal. UHF decreases that effect. Although it may not travel as far, UHF radio waves will get through obstacles better than VHF.
To highlight the differences in indoor range, below is an excerpt from a brochure from a leading two-way radio manufacturer on the expected range of one of their lines of portable VHF and UHF two-way radios:
“Coverage Estimates: At full power, line-of-sight, with no obstructions, range is approximately 4 miles or more. Indoor coverage on VHF is approximately 270,000 sq. ft. and 300,000 sq. ft. on UHF. Expect a vertical coverage of approximately 20 stories on VHF and more to 30 stories on UHF. Note: Range and coverage are estimates and not guaranteed.”
VHF waves are not very good at finding their way around walls, buildings, and rugged landscapes. Therefore, the range will be significantly reduced for VHF radios in these environments. That may not necessarily be a problem if the range needed is only a few hundred feet. You can also add an external antenna to an indoor VHF base station which will reduce or eliminate this problem.
One of the downsides to UHF is that the FCC requires you to obtain a license to operate on these frequencies. Although many frequencies in the commercial VHF band also require a license. If you choose a radio on the VHF MURS frequencies, you can operate it without a license. UHF equipment is usually more expensive. Components must be precisely fitted and are more expensive to build. This doesn’t mean it’s necessarily better, just more expensive.
An advantage of UHF transmission is the physically short wave that the high frequency produces. That means the radio’s antenna can be shorter than an equivalent VHF radio.
VHF broadcaster
VHF equipment operates between the 30 MHz and 300 MHz frequencies. FM radio, two-way radios, and television broadcasts operate in this range.
Both UHF and VHF radios are prone to line-of-sight factors, but VHF a bit more. The waves get through trees and rugged landscapes, but not as well as UHF frequencies do. However, if a VHF wave and a UHF wave were transmitted over an area with no barriers, the VHF wave would travel almost twice as far. This makes VHF easier to transmit over a long range. If you work primarily outdoors, a VHF radio is probably the best option, especially if you’re using a base station radio indoors and adding the external antenna.
Since VHF has been around longer and is not as complicated to manufacture, the equipment is often cheaper compared to similar UHF equipment. A disadvantage of this equipment may be its size. Since the frequency waves are larger, an antenna must be larger.
VHF radios also have fewer frequencies available. Interference with other radios is more likely to be a problem. However, the FCC recently made this less of an issue when they opened up the MURS frequencies. The 150 MHz frequency is a Citizen Band radio spectrum that is called the MURS service. MURS stands for Multiple Use Radio Service. This service is for use in the United States and Canada. It is a low power and short range service in the VHF 150 MHz Citizen Band radio spectrum. There are 5 channels on the MURS frequencies with 38 privacy codes below each allowing you to pick up conversations with just your code. The FCC does not require users of products for MURS to be licensed.
With MURS you can add a larger or external antenna to improve the range. If you want to put an antenna on top of your house or business, you can do it with MURS. Some antenna manufacturers claim that an external antenna can increase a transmitter’s effective radiated power by a factor of 4. These MURS intercoms can transmit up to four miles, and perhaps more with an external antenna depending on terrain.
An advantage of VHF wireless radios is that battery life is almost always better than similar UHF units. For hand radios this is an advantage.
VHF equipment is often lower cost for those on a budget. The equipment can be cheaper than similar UHF products.
In short, if you plan to use your two-way radios primarily inside buildings, UHF is probably the best solution for you. If you are primarily using your two-way radios to communicate with the outside world, VHF would be a good choice. Any of the radio technologies can work for you if you don’t really have a long range to cover. In that case, you may want to choose VHF for its lower cost.