Does uhf go through walls?

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (one decimeter). Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF (very high frequency) or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications.

The IEEE defines the UHF radar band as frequencies between 300 MHz and 1 GHz. Two other IEEE radar bands overlap the ITU UHF band: the L band between 1 and 2 GHz and the S band between 2 and 4 GHz.

Radio waves in the UHF band travel almost entirely by line-of-sight propagation (LOS) and ground reflection; unlike in the HF band there is little to no reflection from the ionosphere (skywave propagation), or ground wave. UHF radio waves are blocked by hills and cannot travel beyond the horizon, but can penetrate foliage and buildings for indoor reception. Since the wavelengths of UHF waves are comparable to the size of buildings, trees, vehicles and other common objects, reflection and diffraction from these objects can cause fading due to multipath propagation, especially in built-up urban areas. Atmospheric moisture reduces, or attenuates, the strength of UHF signals over long distances, and the attenuation increases with frequency. UHF TV signals are generally more degraded by moisture than lower bands, such as VHF TV signals.

Since UHF transmission is limited by the visual horizon to 30–40 miles (48–64 km) and usually to shorter distances by local terrain, it allows the same frequency channels to be reused by other users in neighboring geographic areas (frequency reuse). Radio repeaters are used to retransmit UHF signals when a distance greater than the line of sight is required.

Occasionally when conditions are right, UHF radio waves can travel long distances by tropospheric ducting as the atmosphere warms and cools throughout the day.

The length of an antenna is related to the length of the radio waves used. Due to the short wavelengths, UHF antennas are conveniently stubby and short; at UHF frequencies a quarter-wave monopole, the most common omnidirectional antenna is between 2.5 and 25 cm long. UHF wavelengths are short enough that efficient transmitting antennas are small enough to mount on handheld and mobile devices, so these frequencies are used for two-way land mobile radio systems, such as walkie-talkies, two-way radios in vehicles, and for portable wireless devices; cordless phones and cell phones. Omnidirectional UHF antennas used on mobile devices are usually short whips, sleeve dipoles, rubber ducky antennas or the planar inverted F antenna (PIFA) used in cellphones. Higher gain omnidirectional UHF antennas can be made of collinear arrays of dipoles and are used for mobile base stations and cellular base station antennas.

The short wavelengths also allow high gain antennas to be conveniently small. High gain antennas for point-to-point communication links and UHF television reception are usually Yagi, log periodic, corner reflectors, or reflective array antennas. At the top end of the band, slot antennas and parabolic dishes become practical. For satellite communication, helical and turnstile antennas are used since satellites typically employ circular polarization which is not sensitive to the relative orientation of the transmitting and receiving antennas. For television broadcasting specialized vertical radiators that are mostly modifications of the slot antenna or reflective array antenna are used: the slotted cylinder, zig-zag, and panel antennas.

UHF television broadcasting fulfilled the demand for additional over-the-air television channels in urban areas. Today, much of the bandwidth has been reallocated to land mobile radio system, trunked radio and mobile telephone use. UHF channels are still used for digital television.

Since at UHF frequencies transmitting antennas are small enough to install on portable devices, the UHF spectrum is used worldwide for land mobile radio systems, two-way radios used for voice communication for commercial, industrial, public safety, and military purposes. Examples of personal radio services are GMRS, PMR446, and UHF CB. Some wireless computer networks use UHF frequencies. The widely adopted GSM and UMTS cellular networks use UHF cellular frequencies.

Major telecommunications providers have deployed voice and data cellular networks in VHF/UHF range. This allows mobile phones and mobile computing devices to be connected to the public switched telephone network and the Internet. Satellite phones also use this frequency in the L band and S band.

UHF radars are said to be effective at tracking stealth fighters, if not stealth bombers.

Wi-Fi operates at 2412 MHz-2484 MHz. LTE also operates on UHF frequencies

UHF channels are used for digital television broadcasting on both over the air channels and cable television channels. Since 1962, UHF channel tuners (at the time, channels 14–83) have been required in television receivers by the All-Channel Receiver Act. However, because of their more limited range, and because few sets could receive them until older sets were replaced, UHF channels were less desirable to broadcasters than VHF channels (and licenses sold for lower prices).

A complete list of US Television Frequency allocations can be found at Pan-American television frequencies.

There is a considerable amount of lawful unlicensed activity (cordless phones, wireless networking) clustered around 900 MHz and 2.4 GHz, regulated under Title 47 CFR Part 15. These ISM bands – frequencies with a higher unlicensed power permitted for use originally by Industrial, Scientific, Medical apparatus – are now some of the most crowded in the spectrum because they are open to everyone. The 2.45 GHz frequency is the standard for use by microwave ovens, adjacent to the frequencies allocated for Bluetooth network devices.

The spectrum from 806 MHz to 890 MHz (UHF channels 70–83) was taken away from TV broadcast services in 1983, primarily for analog mobile telephony.

In 2009, as part of the transition from analog to digital over-the-air broadcast of television, the spectrum from 698 MHz to 806 MHz (UHF channels 52–69) was removed from TV broadcasting, making it available for other uses. Channel 55, for instance, was sold to Qualcomm for their MediaFLO service, which was later sold to AT&T, and discontinued in 2011. Some US broadcasters had been offered incentives to vacate this channel early, permitting its immediate mobile use. The FCC's scheduled auction for this newly available spectrum was completed in March 2008.

All wireless communication systems, including cell phones and two-way radios, operate on what is known as operating frequency. The government regulates these frequencies and the equipment used to communicate through them. Since people need all different types of radio signals a variety of wireless equipment is necessary to satisfy all needs.

In the United States, the Federal Communication Commission (FCC) regulates the radio frequency bands. According to US frequency groups there are four different categories: low-band VHF (49-108 MHz), high-band VHF (169-216 MHz), low-band UHF (450-806 MHz), and high-band UHF (900-952 MHz).

The FCC is in control of who operates within each specific band and if anyone has priority over other operators. The primary users are properly licensed radio and television broadcasters as well as commercial communication services such as cell phones and two-way radios.

VHF and UHF each include their own unique benefits and drawbacks.

Very high frequency is commonly used for FM radio broadcast, two-way land mobile radio systems, long-range data communication, and marine communications, just to name a few. VHF includes radio waves from 30 MHz to 300 MHz.

VHF waves must not exceed the local radio horizon of 100 miles. VHF frequencies are less likely to be interrupted by atmospheric noise, issues with electrical equipment, and other interferences.

There are different bands within VHF frequency, including low-band and high-band. Low-band VHF range of 49 MHz includes transmission of wireless microphones, cordless phones, radio controlled toys and more. Slightly higher VHF range of 54-72 MHz operates television channels 2-4, as well as wireless systems defined as “assistive listening.” VHF frequencies 76-88 MHz operate channels 5 and 6. The highest low band VHF is 88-108 MHz and operates the commercial FM radiobroadcast band.

With so many different users the low-band VHF is not recommended for use of serious applications due to the levels of radio “noise” present at these frequencies. Despite the potential background noise this a popular option because of the low cost equipment. Transmission power is limited to under 50 mW, unless you are operating an assistive listening system in the 72-76 MHz range. Also, a large antenna booster is necessary, measuring as much as 3 feet in length, thus limiting portability.

High-band VHF range is popular for professional applications. The lowest high-band (169- 172 MHz) includes 8 different frequencies designated by the FCC, and is often used by the general public and wireless microphone devices. These frequencies are known as “traveling frequencies” because they can be used all around the US without fear of interference from broadcast television. Power is limited to 50 mW, although antenna size is smaller (around 20 inches per ¼ wavelength type). Businesses, government operations and the Coast Guard operate on this “traveling” band. For best results you typically only want to operate two to three units on this frequency.

The high-band VHF between 174 and 216 MHz is used for VHF television channels 7-13. High quality audio is possible as well as smaller antenna size, down to 14 inches or less. The same 50 mW power restrictions apply.

Low-band VHF frequencies are far more likely to incur interferences than high-band VHF frequencies. (Reference)

UHF radio waves are much shorter in length than VHF, measuring around 12 to 24 inches. As a result antenna length is reduced as well as radio range. Anything from a building to a human body can interfere with UHF transmissions. Dropouts and interferences are far more likely, but greater bandwidth occupation is permitted. As a result you may find a wider frequency range as well as wider range of audio signal. Up to 250 mW is allowed, exceeding the 50 mW power restrictions applied to VHF.

Low-band UHF overlaps with high-band UHF, low is 450-536 MHz and high is 470-806 MHz. Typically, business services and UHF television channels 14 through 69 operate using these frequencies. High-band UHF (anything above 900 MHz) offers the least amount of disturbances and requires antennas measuring between 3 and 4 inches. These channels operate studio-to-transmitter links as well as other primary users and additional channels.

UHF radio waves generally only go as far as line of sight. Anything in the way of your sight will also interfere with frequency range, such as buildings, tall trees or any other obstruction. The transmission is high enough to penetrate through building walls, making indoor reception a possibility.  It is the limited line-of-sight broadcast range that makes UHF unsuitable in some instances. VHF offers a much larger broadcast range, which is preferred in some industries.

UHF radio signals are used in many facets of life including satellite communication, GPS, Wi-Fi, Bluetooth, walkie-talkies, cordless phones, cell phones, and television broadcasting.

A large advantage of UHF transmission is the short wavelengths produced by the high frequency.  The size of the radio wave relates directly to the length of transmission as well as the reception antennas. In general, UHF antennas are short and wide.

UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception.

Hello, My name is Mike P. and this is my question.

If radio & light waves are both properties of the electromagnetic spectrum then why can radio waves pass through walls but light cannot?

Thank You

Hello Mike P.,

PART 1.

Let me first make sure the terminology we use is right.

The words "electromagnetic spectrum" are used to name a group of waves. Not any kind of waves, ( not acoustic, not mechanical waves) but electromagnetic waves. These waves have in COMMON that they are originated by electric or magnetic processes. But they also DIFFER in something which is called WAVELENGTH. (Simply speaking, their size.)

Check out our pages of light on the following web page

http://www.fnal.gov/pub/inquiring/more/light/index.html

( As an analogy think about "senior class". It is a name for a bunch of kids going to the same school and being roughly about the same age. However, they are all different. The differ in their weight.) RADIO waves and LIGHT waves are both PART of the "ELECTROMAGNETIC SPECTRUM", just as say JUDY and JOHN are PART of the "SENIOR CLASS".

Got the analogy?

Great!

PART 2.

Ok, now let us take a look at your question. I decided to give you two answers. One intuitive and not very precise, but still demonstrating the idea, and a second one, more precise and scientific.

PART2A.

The first answer uses again an analogy:

radio waves corresponding to a boy light waves corresponding to a mosquito the wall corresponding to rain

The answer to your question is hidden in the comparison of the sizes of the above objects.

A boy can easily run when it is rainy. Right? But a mosquito will never fly when it is rainy. Why? Because the size of a mosquito is roughly the same as the size of a rain drop.

If a mosquito entered into the rain, the first few drops would knock the mosquito down to the mud. On the other hand, since the size of a boy is much much bigger than the size of a rain drop, it is easy for a boy to run on the street even if it is rainy.

Now I show you how to use the above example in the case of the waves and the wall. What do you compare in this case?

You compare the size of the waves and a typical size of atoms in the wall.

The size of the waves is characterized by their wavelength.

I am telling you, radio waves are huge waves, their wavelengths are much much bigger then the size of atoms in the wall. According to the above analogy, that is why they go easily through the wall. ( As a boy did in the rain.)

On the other side, light waves are very very small waves, their size ( wavelength ) is comparable to the size of atoms in the wall. And that is why they are not able to go through the wall. ( As a mosquito cannot fly when it is rainy.)

CONCLUSION1: The radio and light waves are part of the electromagnetic spectrum, but are very different. Radio waves are much bigger than light waves (in terms of their wavelength). Radio waves are bigger then the size of atoms in a wall, that is why they go through, while light is a small wave and cannot get through the wall.

Does this make sense to you?

Good!

PART2B.

Before I give you a more precise answer, let us examine what you said. You claim:

"Radio waves go through the wall and light does not."

WELL, THIS IS NOT NECESSARILY TRUE ALL THE TIME!!!

If the wall is made out of glass, LIGHT WILL go through it.

On the other hand, if the wall is made out of iron, the radio waves WILL NOT go through the wall!!! appears

Wow, things are starting to be complicated right?

PART2C.

This leads us to a more precise answer to your question than the one I gave you above in PART2A. The real key is hidden in the STRUCTURE of the WALL. It matters, what the wall is made from, what kinds of atoms and molecules are its constituents. Also it is very important HOW these atoms in the wall are tight together.

As you know, every atom has a shell of electrons. These electrons interact between each of other and also interact with the outside world. The properties of these electrons dictate, whether a certain kind of incoming electromagnetic wave will go through or will not.

Some materials have the electron structure such, that they to be transparent for light but not for ultraviolet radiation ( for example glass, you will never get sun burned behind a window). But you can safely listen radio in your room. Glass is transparent to radio waves.

Some other materials have a different electron structure of their atoms, so they are not transparent for light, but are transparent for radio waves. Let us say a brick wall.

Also, as I said, you can find materials ( conductors, such as gold, iron, silver) that are neither transparent for radio waves nor for light.

CONCLUSION2: The atomic structure, especially the properties of the electron shells of atoms in the wall dictate if that particular wall to be transparent or not for a certain type of electromagnetic wave.

Hope, my answer satisfies your curiosity. Please keep wondering and asking questions. That is how you will learn the most about our world.

Arnold Pompos Graduate Student at Fermilab