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Wave filterVHF (Very High Frequency) and UHF (Ultra High Frequency) come with distinct pros and cons, understanding these differences will help you identify the best signal frequency for your two-way radio needs. For instance, UHF does not travel as far as VHF but may grant higher bandwidth occupation.

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.

VHF- Very High Frequency

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- Ultra High Frequency

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.

The cost of operating UHF equipment outweighs the operation of VHF equipment.This is because it is more work to create UHF compatible devices based on the ways high frequency and short wavelength radio signals interact together. The difference in cost largely relates to the need for antennas, cables and other additional equipment. 

Need help identifying the best radio frequency for your needs? Contact Highland Wireless today and speak with leading experts regarding two-way radio technology.

Sours: https://www.highlandwireless.com/the-differences-between-uhf-and-vhf-radio-frequencies/

Choosing the correcttwo-way radio frequency is essential to clear communication on your job-site. Knowing your environment will help determine which two-way radios your workforce needs for smooth operation.

Our team can help you decide which two-way radios are best for your business. Here are three questions to ask yourself first:

1. What is Your Existing Radio System Frequency?

In order for your two-way radios to operate effectively, you must stay within the same frequency band. If you are currently using UHF two-way radios in Philadelphia and want to add more to your fleet, purchasing new UHF two-way radios is essential. Our Philadelphia UHF two-way dealers can help you determine what two-way radios will operate on your dedicated frequency.

2. Is Your Radio System Analog or Digital?

Although newer systems are digital, it’s important to confirm what radio system your current fleet operates on. Even different digital brands can be incompatible with each other. Taking stock of your current equipment will help determine which Motorola UHF or VHF two-way radios in Philadelphia are right for your business.

3. Where Will You Be Using Your Two-Way Radios?

Lower frequency means longer wavelength. VHF radios are suited for long distances in and outdoor use. UHF radios operate at a higher frequency. This makes them ideal for wireless communications that need to penetrate through buildings, walls, or concrete. UHF radios are suited for indoor communication solutions, where obstacles are easily penetrable.

Sours: https://www.wirelessinc.com/difference-between-uhf-and-vhf-two-way-radios-in-philadelphia-wireless-inc/
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Very high frequency

Electromagnetic wave range of 30-300 MHz

"VHF" redirects here. For the diseases, see Viral hemorrhagic fever.

Frequency range

30 MHz to 300 MHz

Wavelength range

10 to 1 m

Very high frequency (VHF) is the ITU designation[1] for the range of radio frequencyelectromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).

VHF radio waves propagate mainly by line-of-sight, so they are blocked by hills and mountains, although due to refraction they can travel somewhat beyond the visual horizon out to about 160 km (100 miles). Common uses for radio waves in the VHF band are Digital Audio Broadcasting (DAB) and FM radio broadcasting, television broadcasting, two-wayland mobile radio systems (emergency, business, private use and military), long range data communication up to several tens of kilometers with radio modems, amateur radio, and marine communications. Air traffic control communications and air navigation systems (e.g. VOR & ILS) work at distances of 100 kilometres (62 mi) or more to aircraft at cruising altitude.

In the Americas and many other parts of the world, VHF Band I was used for the transmission of analog television. As part of the worldwide transition to digital terrestrial television most countries require broadcasters to air television in the VHF range using digital rather than analog format.

Propagation characteristics[edit]

Radio waves in the VHF band propagate mainly by line-of-sight and ground-bounce paths; unlike in the HF band there is only some reflection at lower frequencies from the ionosphere (skywave propagation).[2] They do not follow the contour of the Earth as ground waves and so are blocked by hills and mountains, although because they are weakly refracted (bent) by the atmosphere they can travel somewhat beyond the visual horizon out to about 160 km (100 miles). They can penetrate building walls and be received indoors, although in urban areas reflections from buildings cause multipath propagation, which can interfere with television reception. Atmospheric radio noise and interference (RFI) from electrical equipment is less of a problem in this and higher frequency bands than at lower frequencies. The VHF band is the first band at which efficient transmitting antennas are small enough that they can be mounted on vehicles and portable devices, so the band is used for two-wayland mobile radio systems, such as walkie-talkies, and two way radio communication with aircraft (Airband) and ships (marine radio). Occasionally, when conditions are right, VHF waves can travel long distances by tropospheric ducting due to refraction by temperature gradients in the atmosphere.

Line-of-sight calculation[edit]

For analog TV, VHF transmission range is a function of transmitter power, receiver sensitivity, and distance to the horizon, since VHF signals propagate under normal conditions as a near line-of-sight phenomenon. The distance to the radio horizon is slightly extended over the geometric line of sight to the horizon, as radio waves are weakly bent back toward the Earth by the atmosphere.

An approximation to calculate the line-of-sight horizon distance (on Earth) is:

These approximations are only valid for antennas at heights that are small compared to the radius of the Earth. They may not necessarily be accurate in mountainous areas, since the landscape may not be transparent enough for radio waves.

In engineered communications systems, more complex calculations are required to assess the probable coverage area of a proposed transmitter station.[citation needed]

The accuracy of these calculations for digital TV signals is being debated.[3]

Antennas[edit]

See also: UHF television broadcasting § UHF vs VHF

A VHF television broadcasting antenna. This is a common type called a super turnstile or batwing antenna.

VHF is the first band at which wavelengths are small enough that efficient transmitting antennas are short enough to mount on vehicles and handheld devices, a quarter wave whip antenna at VHF frequencies is 25 cm to 2.5 meter (10 inches to 8 feet) long. So the VHF and UHF wavelengths are used for two-way radios in vehicles, aircraft, and handheld transceivers and walkie-talkies. Portable radios usually use whips or rubber ducky antennas, while base stations usually use larger fiberglass whips or collinear arrays of vertical dipoles.

For directional antennas, the Yagi antenna is the most widely used as a high gain or "beam" antenna. For television reception, the Yagi is used, as well as the log-periodic antenna due to its wider bandwidth. Helical and turnstile antennas are used for satellite communication since they employ circular polarization. For even higher gain, multiple Yagis or helicals can be mounted together to make array antennas. Vertical collinear arrays of dipoles can be used to make high gain omnidirectional antennas, in which more of the antenna's power is radiated in horizontal directions. Television and FM broadcasting stations use collinear arrays of specialized dipole antennas such as batwing antennas.

Universal use[edit]

Certain subparts of the VHF band have the same use around the world. Some national uses are detailed below.

By country[edit]

Australia[edit]

See also: Australasian television frequencies

The VHF TV band in Australia was originally allocated channels 1 to 10-with channels 2, 7 and 9 assigned for the initial services in Sydney and Melbourne, and later the same channels were assigned in Brisbane, Adelaide and Perth. Other capital cities and regional areas used a combination of these and other frequencies as available. The initial commercial services in Hobart and Darwin were respectively allocated channels 6 and 8 rather than 7 or 9.

By the early 1960s it became apparent that the 10 VHF channels were insufficient to support the growth of television services. This was rectified by the addition of three additional frequencies-channels 0, 5A and 11. Older television sets using rotary dial tuners required adjustment to receive these new channels. Most TVs of that era were not equipped to receive these broadcasts, and so were modified at the owners' expense to be able to tune into these bands; otherwise the owner had to buy a new TV.

Several TV stations were allocated to VHF channels 3, 4 and 5, which were within the FM radio bands although not yet used for that purpose. A couple of notable examples were NBN-3Newcastle, WIN-4Wollongong and ABCNewcastle on channel 5. While some Channel 5 stations were moved to 5A in the 1970s and 80s, beginning in the 1990s, the Australian Broadcasting Authority began a process to move these stations to UHF bands to free up valuable VHF spectrum for its original purpose of FM radio. In addition, by 1985 the federal government decided new TV stations are to be broadcast on the UHF band.

Two new VHF, 9A and 12, have since been made available and are being used primarily for digital services (e.g. ABC in capital cities) but also for some new analogue services in regional areas. Because channel 9A is not used for television services in or near Sydney, Melbourne, Brisbane, Adelaide or Perth, digital radio in those cities are broadcast on DAB frequencies blocks 9A, 9B and 9C.

VHF radio is also used for marine Radio[4] as per its long-distance reachability comparing UHF frequencies.

Example allocation of VHF–UHF frequencies:[5]

  • Radionavigation 60: 84–86 MHz
  • Fixed Maritime Mobile: 130–135.7 MHz
  • Fixed Aeronautical radio navigation: 160–190 MHz
  • Broadcasting Aeronautical Radionavigation: 255–283.5 MHz
  • Aeronautical Radionavigation AUS 49 / Maritime Radionavigation (radiobeacons) 73: 315–325 MHz

New Zealand[edit]

  • 44–51, 54–68 MHz: Band I Television (channels 1–3)
  • 87.5–108 MHz: Band II Radio
  • 174–230 MHz: Band III Television (channels 4–11)

Until 2013, the four main Free-to-Air TV stations in New Zealand used the VHF Television bands (Band I and Band III) to transmit to New Zealand households. Other stations, including a variety of pay and regional free-to-air stations, were forced to broadcast in the UHF band, since the VHF band had been very overloaded with four stations sharing a very small frequency band, which was so overcrowded that one or more channels would not be available in some smaller towns.

However, at the end of 2013, all television channels stopped broadcasting on the VHF bands, as New Zealand moved to digital television broadcasting, requiring all stations to either broadcast on UHF or satellite (where UHF was unavailable) utilising the Freeview service.[6]

Refer to Australasian television frequencies for more information.

United Kingdom[edit]

British television originally used VHF band I and band III. Television on VHF was in black and white with 405-line format (although there were experiments with all three colour systems-NTSC, PAL, and SECAM-adapted for the 405-line system in the late 1950s and early 60s).

British colour television was broadcast on UHF (channels 21–69), beginning in the late 1960s. From then on, TV was broadcast on both VHF and UHF (VHF being a monochromatic downconversion from the 625-line colour signal), with the exception of BBC2 (which had always broadcast solely on UHF). The last British VHF TV transmitters closed down on January 3, 1985. VHF band III is now used in the UK for digital audio broadcasting, and VHF band II is used for FM radio, as it is in most of the world.

Unusually, the UK has an amateur radio allocation at 4 metres, 70-70.5 MHz.

United States and Canada[edit]

Frequency assignments between US and Canadian users are closely coordinated since much of the Canadian population is within VHF radio range of the US border. Certain discrete frequencies are reserved for radio astronomy. The general services in the VHF band are:

  • 30–49.6 MHz: Licensed 2-way land mobile communication, with various sub-bands.[a]
  • 30–88 MHz: Military VHF FM, including SINCGARS
  • 43–50 MHz: Cordless telephones, 49 MHz FM walkie-talkies and radio controlled toys, and mixed 2-way mobile communication. The FM broadcast band originally operated here (42–50 MHz) before it was moved to 88–108 MHz.
  • 50–54 MHz: Amateur radio6-meter band
  • 54–88 MHz, known as "Band I" internationally; some DTV stations will appear here. See North American broadcast television frequencies
    • 54–72 MHz TV channels 2–4 (VHF-Lo)
    • 72–76 MHz: Radio controlled models, industrial remote control, and other devices. Model aircraft operate on 72 MHz while surface models operate on 75 MHz in the US and Canada, air navigation beacons 74.8–75.2 MHz.
    • 76–88 MHz TV channels 5–6 (VHF-Lo)
  • 87.5–108 MHz: FM radio broadcasting (87.9–91.9 non-commercial, 92–108 commercial in the United States) (known as "Band II" internationally)
  • 108–118 MHz: Air navigation beacons VOR
  • 118–137 MHz: Airband for air traffic control, AM
    • 121.5 MHz is an emergency frequency
  • 137–138 MHz Space research, space operations, meteorological satellite[8]
  • 138–144 MHz: Land mobile, auxiliary civil services, satellite, space research, and other miscellaneous services
  • 144–148 MHz: Amateur radio2-meter band
  • 148–150 MHz: Land mobile, fixed, satellite
  • 150–156 MHz: "VHF business band," public safety, the unlicensed Multi-Use Radio Service (MURS), and other 2-way land mobile, FM
  • 156–158 MHz VHF Marine Radio
    • 156.8 MHz (Channel 16) is the maritime emergency and contact frequency.
  • 159.81-161.565 MHz railways [b]
    • 159.81–160.2 are railroads in Canada only and is used by trucking companies in the U.S.
  • 160.6–162 Wireless microphones and TV/FM broadcast remote pickup
  • 162.4–162.55: NOAA Weather Stations, narrowband FM, Weatheradio Canada Stations
  • 174–240 MHz, known as "Band III" internationally. A number of DTV channels have begun broadcasting here, especially many of the stations which were assigned to these channels for previous analog operation.
    • 174–216 MHz television channels 7–13 (VHF-Hi)
    • 174–216 MHz: professional wireless microphones (low power, certain exact frequencies only)
    • 216–222 MHz: land mobile, fixed, maritime mobile,[8]
    • 222–225 MHz: 1.25 meters (US) (Canada 219–220, 222–225 MHz) amateur radio
  • 225 MHz and above (UHF): Military aircraft radio, 243 MHz is an emergency frequency (225–400 MHz) AM, including HAVE QUICK, dGPS RTCM-104

Cable television, though not transmitted aerially, uses a spectrum of frequencies overlapping VHF.[9]

VHF television[edit]

The U.S. FCC allocated television broadcasting to a channelized roster as early as 1938 with 19 channels. That changed three more times: in 1940 when Channel 19 was deleted and several channels changed frequencies, then in 1946 with television going from 18 channels to 13 channels, again with different frequencies, and finally in 1948 with the removal of Channel 1 (analog channels 2-13 remain as they were, even on cable television).[10] Channels 14-19 later appeared on the UHF band, while channel 1 remains unused.

87.5–87.9 MHz[edit]

87.5–87.9 MHz is a radio frequency which, in most of the world, is used for FM broadcasting. In North America, however, this bandwidth is allocated to VHF television channel 6 (82–88 MHz). The analog audio for TV channel 6 is broadcast at 87.75 MHz (adjustable down to 87.74). Several stations, known as Frankenstations, most notably those joining the Pulse 87 franchise, have operated on this frequency as radio stations, though they use television licenses. As a result, FM radio receivers such as those found in automobiles which are designed to tune into this frequency range could receive the audio for analog-mode programming on the local TV channel 6 while in North America. The practice largely ended with the DTV transition in 2009, although some still exist.

The FM broadcast channel at 87.9 MHz is normally off-limits for FM audio broadcasting; it is reserved for displaced class D stations which have no other frequencies in the normal 88.1–107.9 MHz subband to move to. So far, only two stations have qualified to operate on 87.9 MHz: 10–watt KSFH in Mountain View, California and 34–watt translator K200AA in Sun Valley, Nevada.

Unlicensed operation[edit]

In some countries, particularly the United States and Canada, limited low-power license-free operation is available in the FM broadcast band for purposes such as micro-broadcasting and sending output from CD or digital media players to radios without auxiliary-in jacks, though this is illegal in some other countries. This practice was legalised in the United Kingdom on 8 December 2006.[11]

See also[edit]

Notes[edit]

  1. ^The 42 MHz Segment is still in current use by the California Highway Patrol, New Jersey State Police, Tennessee Highway Patrol, and other state law enforcement agencies.
  2. ^The 160 and 161 areas are Association of American Railroads (AAR) 99 channel railroad radios, issued to the railroad. For example, AAR 21 is 160.425 MHz and that is issued to Tennessee Valley Railroad Museum, as well as other railroads that want AAR Channel 21.

References[edit]

Radio spectrum (ITU)

ELF
3 Hz/100 Mm
30 Hz/10 Mm

SLF
30 Hz/10 Mm
300 Hz/1 Mm

ULF
300 Hz/1 Mm
3 kHz/100 km

VLF
3 kHz/100 km
30 kHz/10 km

LF
30 kHz/10 km
300 kHz/1 km

MF
300 kHz/1 km
3 MHz/100 m

HF
3 MHz/100 m
30 MHz/10 m

VHF
30 MHz/10 m
300 MHz/1 m

UHF
300 MHz/1 m
3 GHz/100 mm

SHF
3 GHz/100 mm
30 GHz/10 mm

EHF
30 GHz/10 mm
300 GHz/1 mm

THF
300 GHz/1 mm
3 THz/0.1 mm

Analog televisionbroadcasting topics

Systems
  • 180-line
  • 405-line (System A)
  • 441-line
  • 525-line (System J, System M)
  • 625-line (System B, System C, System D, System G, System H, System I, System K, System L, System N)
  • 819-line ( System E , System F )
Color systems
Video
Sound
Modulation
Transmission
Frequencies & Bands
Propagation
Testing
Artifacts
Sours: https://en.wikipedia.org/wiki/Very_high_frequency
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