UHF versus VHF: Which Two-Way Radio Frequency Is Better?
There are two main formats for two-way radios. They are ultra high frequency (UHF) radio and 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 is equal to 1,000 cycles per second, or megahertz (MHz), which is equal to 1,000,000 cycles per second, or 1,000 kHz. The relationship between these units is like this: 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 cycle peaks, frequency refers to the time measured between the “crest” and the “trough” of a wave reaching the source. So frequency measures time rather than distance, but essentially they both say the same thing.
The important thing about the wavelength of 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’ve read above, you may think that VHF is always the best choice for a two-way radio, no matter where you’re 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 earlier conversation about wavelength? 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 door. Metal is an enemy of radio waves and they do not normally pass through it.
For our example, let’s assume that the UHF wavelength the radio uses is about one and a half feet long and that 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 foot-and-a-half wave will pass through the gate, since the gate is wider than the wavelength. The VHF signal will be fully reflected as it is wider than the door opening.
Your microwave oven is an example of this. The glass entrance door has a metal mesh with very small holes. Microwaves, which are 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 five foot wide pole. You will encounter the same challenges that a VHF signal encounters. Now imagine walking through the building with a pole only one and a half feet wide like a UHF wave. There are far fewer doors that you couldn’t get through.
The only difference is that the wireless signals will penetrate through drywall, masonry, human bodies, furniture, wall panels, 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 penetrate these obstacles better than UHF, but that doesn’t necessarily mean that VHF is better for indoor applications, as we’ll talk about 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 surround it. Lower frequencies, such as VHF, diffract around large smooth obstacles more easily, and they also travel more easily through bricks and stones.
For most applications, lower radio frequencies are better for a longer range. A television station illustrates it. 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.
Therefore, there is no clear choice for which is better, VHF or UHF. There is a lot of “black magic” in radio technology, so it is 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 included below.
UHF radio
UHF equipment operates between the frequencies of 300 MHz and 3000 MHz. Until recently, it was not used much. 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 a new VHF frequency called MURS that is not used much in most areas so far. There is more information on MURS below in the VHF section. If you are in an area where interference from other radios can be a problem, UHF transmitters and receivers might be your best option unless you are using a MURS VHF radio. UHF is best for traversing physical barriers such as walls, buildings, and rugged landscapes. Anything that obstructs a radio wave will weaken the radio signal. UHF lessens that effect. Although it may not travel that far, UHF radio waves will pass through obstacles better than VHF.
To highlight the differences in range indoors, here is an excerpt from a brochure from a leading manufacturer of two-way radios on the intended range of one of their VHF and UHF two-way portable radio lines:
“Coverage Estimates: At full power, with line of sight, unobstructed, range is approximately 4+ miles. Indoor coverage on VHF is approximately 270,000 square feet and 300,000 square feet on UHF. Expect approximately 20 floors vertical coverage in VHF and more than 30 floors in UHF. Note: Range and coverage are estimates and are not guaranteed. “
VHF waves are not very good at navigating between 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 required reach 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 fit precisely and are more expensive to build. This does not mean that it is necessarily better, just more expensive.
An advantage of UHF transmission is the physically short wave that the high frequency produces. That means the radio antenna may be shorter than an equivalent VHF radio.
VHF radio
VHF equipment operates between the frequencies 30 MHz and 300 MHz. 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. Waves cut through trees and rugged landscapes, but not as well as UHF frequencies. However, if a VHF wave and a UHF wave were transmitted over an area without barriers, the VHF wave would travel almost twice as far. This makes VHF easier to transmit over long distances. If you work primarily outdoors, a VHF radio is probably the best option, especially if you are using a base station radio indoors and you add the external antenna.
Since VHF has been around longer and is not that complicated to manufacture, the equipment is usually cheaper compared to similar UHF equipment. A disadvantage of this equipment can 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 a problem when they opened the MURS frequencies. The 150 MHz frequency is a Citizen Band radio spectrum called MURS service. MURS stands for Multi-Use Radio Service. This service is for use in the United States and Canada. It is a low-power, short-range service on the VHF 150 MHz Citizens Band radio spectrum. There are 5 channels on the MURS frequencies with 38 privacy codes underneath each that allow you to pick up only conversations in your code. The FCC does not require users of MURS products to be licensed.
With MURS you can add a larger or external antenna to improve range. If you want to put an antenna on top of your home or business, you can do it with MURS. Some antenna manufacturers claim that an external antenna can increase the effective radiated power of a transmitter by a factor of 4. These MURS intercoms can transmit up to four miles, and perhaps more with an external antenna depending on the terrain.
One benefit of VHF wireless radios is that battery life is almost always better than similar UHF units. For handheld radios, this is an advantage.
VHF equipment is usually less expensive 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, then UHF is probably the best solution for you. If you primarily use your two-way radios to communicate outside, VHF would be a good choice. Either radio technology 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.