VHF, since it tends to bend with the curvature of the earth more than UHF, is ideal for outdoor applications where distance is the primary user need. However, a big disadvantage of VHF is that it does not work well indoors as it will not penetrate walls or reinforced concrete as well as UHF. I will primarily use my radio indoors. Each band has advantages and disadvantages depending on the application. UHF and VHF are the two most commonly used frequency ranges for walkie talkies. Each has its own advantages and disadvantages for wireless microphone operation, based on the designated users of the band, the physical characteristics of the band, and the regulatory limitations of the band. You can get radios that use either UHF (Ultra High Frequency) or VHF (Very High Frequency). But overall, VHF radios are better for outdoor use in large areas, and UHF radios are better for indoor or outdoor settings that are in close proximity. With Amateur Radio VHF and UHF, the power limits are 1500 watts with no radiated power restrictions. Well the UHF signals don't travel quite as far outdoors as VHF signals, but they do a better job of penetrating wood, steel, and concrete, giving you better range and performance in urban environments and around buildings, its a great news that anyone can be helping use to do with the "UHF VHF RADIO" Either VHF or UHF radio technology can work for you if you don’t really have a long range to cover. UHF uses higher frequencies than VHF. Well the UHF signals don't travel quite as far outdoors as VHF signals, but they do a better job of penetrating wood, steel, and concrete, giving you better range and performance in urban environments and around buildings, its a great news that anyone can be helping use to do with the "UHF VHF RADIO" VHF radios offer a larger broadcast range, using radio waves from 30 MHz to 300 MHz. These radio waves travel over line of sight, making them ideal for local communications over a few kilometres. OK, that’s the end of the science lesson. 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. Our Philadelphia radio dealer team is ready to help you find the right equipment that your workers demand. Like the VHF region, the UHF region contains several bands that are used for wireless microphone systems. We supply both UHF and VHF two way radios, but if you're confused about which to ask for, don't panic. However, the disadvantage of UHF is that its range will be less outside when compared to VHF. On the lower portions of VHF, you can talk to Europe, Mediterranean, Northern Africa, etc. VHF Radio. Rating: 0%. This is a very good question to ask as picking the wrong frequency band can lead to problems later. VHF radio waves operate in a band between 30-300 megahertz, while UHF radio signals are propagated within 300 megahertz and 3 gigahertz. Learn more about us. Or fill out the contact us form for support. Radio Depot has been selling and supporting two-way radios since 2005. Signal Propagation - When we refer to signal propagation, we are talking about the radio signal getting from one place to another, presumably from the station's transmitting antenna to the receiver's antenna. Sistemas UHF ágeis de frequência serão uma melhor opção. The primary physical characteristic of UHF radio waves is their much shorter wavelength of 12 inches to 24 inches. UHF. In general, VHF radios operate in the 138-174 MHz frequency band and UHF radios operate in the 400-512 MHz frequency band making UHF roughly three times higher in frequency than VHF. As you can see, each operational frequency comes with its own advantages and disadvantages. Therefore, VHF is most commonly used by farms, rural mining projects or users who are prepared to sacrifice in-building coverage, for better outdoor coverage over longer distances. If you are working mostly outdoors, a VHF radio … 3G mobile networks use more high frequencies of the UHF band. VHF’s frequency range is from 30 MHz to 300 MHz. Unlike VHF radios, CB radios need large antennas, while VHFs are easily portable. UHF and VHF are only two of the several types of frequencies used along the electromagnetic spectrum. The vast majority of these Chinese radios do not have FCC approval for use and, therefore, are not legal for operation in the USA. Very High Frequencies (VHF) have been used for voice and data radio communications since the middle of the last century. 1. However, UHF radios … Isso porque todos os canais de TV VHF e a maioria dos UHF são usados em um lugar ou outro e os conflitos de frequência sempre acabam ocorrendo. Before 2009, in the days of analog TV, most stations were transmitting in VHF.Back then, transmitting in VHF had an advantage because it supported longer transmission distances and was better at cutting through interference.. UHF television broadcasting is the use of ultra high frequency (UHF) radio for over-the-air transmission of television signals.UHF frequencies are used for both analog and digital television broadcasts. However, certain physical, regulatory, and economic differences between VHF and UHF regions should be noted here. Usually channels of UHF have a higher bandwidths than VHF, therefore, carries more information. Get 30 to 40 miles from a FM station and you start to hear static. To expand the range of a handheld device, it needs to be connected to a large CB radio antenna. This allows you to slowly transition to digital without making all older analog radios obsolete. UHF is also the better choice in urban areas with a lot of houses and commercial buildings that the radio signal will be passing thru. What this means is, lower frequencies have longer wavelengths while higher frequencies have shorter wavelengths. In den Warenkorb. How does all of this relate to picking a radio? UHF, or the "mall security band" as some call it are often low power in-house repeaters for in building portable radios rather than wide area repeaters used on VHF for mobile operation. Para obtermos essa resposta, é importante conhecermos melhor o conceito de cada uma dessas tecnologias. If you are using the radio primarily outdoors with clear line-of-sight, then VHF is a better choice because it's signal will travel farther. É a solução ideal para os supervisores monitorarem a situação de segurança dos usuários de rádio que trabalham sozinhos. There are two types of VHF units you can use, both having different characteristics and qualities. Ultra-High Frequency (UHF) Professional level UHF two-way radios have a frequency range between 400-512 MHz. Compare the Difference Between Similar Terms. VHF features 130-174 megahertz, while UHF features 400-520-megahertz. Why the FCC Allocates Frequencies and Why We Need To Stick To Them. Helpful informative posts about two way radios, promotions, and industry solutions. Our Philadelphia radio dealer team is ready to help you find the right equipment that your workers demand. The waves make it through trees and rugged landscapes, but not as well as UHF frequencies do. Although ‘line of sight’ is not necessary UHF waves are more attenuated than VHF waves. VHF Data Radio. Each mode of radio wave propagation is useful in different settings. Electromagnetic waves with the frequency range from 30MHz to 300MHz are called VHF. 2. ; I will use my radio both indoors and outdoors. O que é UHF? UHF (Ultra High Frequency) and  VHF (Very High Frequency) two-way radios each have their advantages and disadvantages. Both UHF and VHF radios are prone to line of sight factors, but VHF a little more so. VHF like AM radio, gives better radio coverage over long distances due to VHF's longer wave length compared with UHF. Why is this important? The wide availability of VHF marine radios and the increased number of recreational sailors means there are a dizzying amount of sets to choose from with vastly different pricing. UHF radios are often smaller than their VHF counter parts but in reality very few parts of a radio actually operate at the assigned UHF or VHF frequencies. VHF radios offer a larger broadcast range, using radio waves from 30 MHz to 300 MHz. Best Ham Radios To Buy When Starting Out. Both of these bands are widely used in wireless television broadcast services. The wide availability of VHF marine radios and the increased number of recreational sailors means there are a dizzying amount of sets to choose from with vastly different pricing. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF). Most public safety agencies in rural counties (Sheriff, Fire, EMS, etc) use VHF radios, especially in areas with low population density and hills and valleys. VHF band (with a length of 270MHz) is much narrower than the UHF band (which has a frequency range of 2700MHz), 3. Another challenge for VHF two-way radios is that they do not travel well when there are obstacles like buildings or heavily forested areas. And the professional lot that have a much longer range and are professionally used. VHF radios have been around for much longer and are quite cheaper compared to UHF. UHF vs VHF - Learn about radio frequencies, Analog vs Digital Radio - 7 Key Differences, Radio 101 - The complete two way radio guide, Radio Programming - 10 Common questions and concerns. VHF. All comments are moderated before being published. UHF band is sandwiched between VHF and SHF (Super High Frequency) bands in spectrum. These higher frequencies can travel in straight lines that are called line of sight signals, unlike frequencies that are below two megahertz. VHF operates at a higher frequency range than HF, usually between 30-300 MHz. We will discuss these advantages and disadvantages in the sections that follow so that you can choose the correct frequency band for your application. Certain applications are better suited to lower frequency, longer wavelength VHF radios while other applications are better served using higher frequency, shorter wavelength UHF radios. Handheld VHF vs Fixed Mount VHF Marine Radios There are two types of VHF units you can use, both having different characteristics and qualities. In general, VHF radios operate in the 138-174 MHz frequency band and UHF radios operate in the 400-512 MHz frequency band making UHF roughly three times higher in frequency than VHF. QM7 – Seven elements Yagi -Uda Antenna – 144MHz. VHF (Very High Frequency) and UHF (Ultra High Frequency) are two radio frequency bands of electromagnetic waves. Therefore, VHF waves can travel longer distances than UHF. What is a Bi-Cone Antenna ? Handheld VHF vs Fixed Mount VHF Marine Radios. QM7 – Seven elements Yagi -Uda Antenna – … 41,19 € Zur Wunschliste hinzufügen. Described below are the VHF and UHF radio frequency bands. Before picking a solution it’s best to understand the different between these two radio options. UHF, sigla para Ultra High Frequency, significa um sistema de frequência ultra alta, que funciona em uma faixa que vai de 300 Mhz até 3 GHz. Im sure I could pass it right now. UHF channels are typically given higher channel numbers, like the US arrangement with VHF channels 2 to 13, and UHF channels numbered 14 to 83. VHF & UHF frequency waves VHF walkie talkies. Compared to UHF’s range, which is 300 MHz to 3000 MHz, it’s clear that VHF has sometimes 10 times longer wavelengths. Call 0800 294 7766 or send an enquiry. @media (max-width: 1171px) { .sidead300 { margin-left: -20px; } } Im englischen Sprachraum wird für Ultrakurzwelle der Begriff VHF (very high … Posted date: October 12, 2020 in: Review. das 2meter funkband ( afu, bos und betriebsfunk)sind im VHF bereich. Frequency range of 300MHz – 3000MHz (or 3GHz) in electromagnetic wave spectrum are known as UHF. Surveyors, hikers, hunters, golf course personnel, farmers and anyone else primarily using their radios outside in rural areas would all be good candidates for VHF radios. The higher the frequency, the shorter the wavelength, the talk distance is reduced but with more penetrating ability. Even in my mobile, I can talk to NY from Virginia on VHF simplex. UHF, with its higher frequencies and shorter wavelengths, will penetrate structures better than VHF so it should be used any time a user needs to communicate indoors, especially when trying to talk thru reinforced concrete structures. Make yourself your antenna for 144MHz Great yagi antenna for 2 meters Band – Download .pdf File – To open file you neeed adobe reader ... Read more . Antenna. VHF radios have been around for much longer than UHF radios … We all want as little disruption to the signal as possible when we receive or transmit messages from our two way radio. Listening to both GMRS and the 2 meter band on my scanner, I can not tell any difference between the efficacy of either. Since television has gone digital, UHF supports more bandwidth, which is good for modern programming with its emphasis on high definition. UHF waves are more affected by attenuation than VHF waves. Entenda o que cada uma significa. A+ A-VHF é a sigla para o termo inglês Very High Frequency (Frequência Muito Alta) que designa a faixa de radiofrequências de 30 a 300 MHz. Best Ham Radios To Buy When Starting Out. 3.1.2 A faixa de freqüências de VHF-AM utilizada no Brasil para comunicações do Serviço Móvel Aeronáutico está compreendida entre 118,000 e 136,975 MHz. This article is going to teach the basics of radio frequencies! That means the antenna on the radio can be shorter than an equivalent VHF radio. Differences of frequency and wavelength between VHF and UHF bands result in unique features for both categories. Indeed, UHF radio frequencies best suit communications within a one kilometre radius – perfect for indoor applications. Sistemas VHF e UHF de frequência fixa (canal único) nas faixas de TV podem não ser boas opções para uso em viagem. UHF radios are commonly used for communication in warehouses, schools and retail stores, indoor security environments etc. Begriff. I've done testing with this andwhen there is a hill in the way of the transmitting station, when they transmit of VHF low band vs, VHF high and UHF their signal becomes less readable the higher you go. Another question that we often get is “Can UHF and VHF radios communicate with each other?”. This is because their wavelengths are much shorter than AM, can penetrate the earth’s atmosphere (so they don’t bounce off of it like AM does) and they travel more in a straight line than AM waves so they are more susceptible to the curvature of the earth. Page 1 of 4 - If GMRS, Then Why VHF/UHF Amateur? But first, we need to talk briefly about the characteristics of both VHF and UHF bands so you will hopefully have a better understanding of which to choose for your particular application. However, VHF radio has weaker building penetration strength compared with UHF. They unfortunately have less channels though, which can lead to congestion and interference from other nearby two-way radios. HF radio, for example, is vital for base stations communicating with each other over vast distances, thanks to ionospheric transmission. UHF waves are more affected by attenuation than VHF waves. Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Coming from Engineering cum Human Resource Development background, has over 10 years experience in content developmet and management. As such, they both offer unique functionality for commercial applications as well as tactical radio usage. 1.UHF radios have a wider range of usable frequencies compared to VHF 2.VHF radio equipment is cheaper compared to UHF 3.VHF radios need a larger antenna compared to UHF radios 4.UHF is better at penetrating barriers compared to VHF … That means with a little elevation, you are talking coast to coast on the higher portions of VHF and the lower portions of UHF. It is also known as the ‘decimeter range’ as the wavelength is in the range from 1 to 10 decimeters. The fundamental difference is in the range of frequencies that they use. All rights reserved. Now that you’re aware of the differences between HF, VHF and UHF radio, you can make an informed decision about which option is a better fit for your business needs. VHF & UHF frequency waves VHF walkie talkies. (adsbygoogle = window.adsbygoogle || []).push({}); Copyright © 2010-2018 Difference Between. Sem esta reinicialização, o rádio muda automaticamente para o modo de emergência com um alerta pedindo ajuda. These UHF radio waves are much shorter in length and pulsate with much more intensity than VHF. Therefore, VHF is most commonly used by farms, rural mining projects or users who are prepared to sacrifice in-building coverage, for better outdoor coverage over longer distances. Diferença entre UHF e VHF Qual será a diferença entre UHF e VHF? Bands withing the frequency range of136-174MHz are used throughout the world for reliable wireless data communications.In the United States and in many other countries, the 136-174 MHz range is used for commercial wireless communications. RV-M7. These bands are divided into small sub-bands called channels. Therefore, VHF waves … Here's real world example that you have probably experienced: If you have listened to an AM radio at night, you typically can hear radio stations many hundreds of miles away from you. FM radio, two-way radios, and television broadcasts operate in this range. - posted in Amateur Radio (Ham): Ive been studying for the Technician exam for a couple of weeks now. VHF radios are best for outdoor use because VHF signals travel farther in open unobstructed areas. When you purchase from us you can expect quality equipment, quick delivery, and a trusted business partner. VHF. Those channels are used for different purposes in different countries. What are the differences between UHF and VHF? This makes VHF easier to broadcast over a long range. 3.1.3 É fortemente recomendado que, a partir de 31 JAN 2005, todos os transceptores de VHF-AM operem com espaçamento máximo de 25 kHz, sob pena dos exploradores de Remember, the lower the frequency, the longer the wavelength, the greater the talk distance but with less penetrating ability. ; I will primarily use my radio outdoors. The longer antennas are more commonly found on VHF radios - they can be uncomfortable for users (e.g. Please call one of our Motorola Master Certified radio consultants at (888) 733-7681 and they will be happy to get you into the correct radio for your needs. What are the benefits of HF radio vs VHF/UHF radios? VHF like AM radio, gives better radio coverage over long distances due to VHF's longer wave length compared with UHF. Real world use shows these radios to be unreliable and often their transmissions are so out of FCC specifications that they can interfere with the other radios in your fleet, or worse, with the radios being used by other organizations around you. GSM networks usually utilize the 900MHz – 1800 MHz band. Confira! Digital is the future of two-way radios but it will be a while yet for the cost of a digital radio … Though the terms VHF (very high frequency) and UHF (ultra-high frequency) are sometimes used interchangeably, they refer to different segments of the electromagnetic spectrum. One of the most frequently asked questions that we receive from customers, especially customers who don’t currently have two-way radios, is “Which Is Better – UHF or VHF?”. June 15, … VHF band (with a length of 270MHz) is much narrower than the UHF band (which has a frequency range of 2700MHz) 3. Beware of cheap Chinese radios that claim to talk over both bands. At the beginning of the low-band VHF range is the 49 MHz region. These transmissions, due to their higher frequency, penetrate through the Ionosphere, with little or no refraction. There are some high-end public safety grade radios than can talk across both bands but they cost many thousands of dollars and are not a practical option for most radio users. Terms of Use and Privacy Policy: Legal. 5. UHF radios are best for indoor use because UHF signals penetrate wood and concrete better. If just through atmosphere, generally, there is more loss at UHF than VHF, but the other things are the dominating factors-both VHF and UHF can easily reach satellites many thousands of miles away when the other factors are removed. VHF / UHF-Mobilfunkstation CRT FP00 Dualband 136-174 und 400-440 MHz Farbe Schwarz, VOX, 128 Kanäle, Scan, Programmierbar, Taschenlampe, FM-Radio, TOT, Repeater . VLF, or very low frequency, includes any audio transmission under 30kHz, while LF, or low frequency, ranges from 30 to 300kHz. 4. security guards) who wear their radio on a belt under their jacket. The answer to this question is NO for most radios. CB vs VHF Radio for RB Use. There is … This type of frequency can be used for both digital and analog broadcasts, and the VHF frequency band runs from 50 MHz to 225 MHz.. What is VHF radio? Ein Frequenzband bezeichnet Frequenzbereiche, also Teilbereiche des elektromagnetischen Spektrums der zur technischen Kommunikation verwendeten elektromagnetischen Wellen. Posted date: October 12, 2020 in: Review. VHF walkies operate on the frequencies between 136 and 174 MHz, they work over large distances with lower power consumption. Last week I purchased a very good GMRS HT with full repeater capability and a mobile antenna. The wavelengths are so long that they sometimes can’t penetrate the earth’s atmosphere so they bounce off and head back down to earth which allows them to travel great distances. VHF band is used for terrestrial communication, and ‘line of sight’ (where transmitter can be seen from receiving antenna without any obstacle) is not necessary. channels 14 through 83 are within the UHF portion of the spectrum. UHF vs. VHF Two-Way Radios VHF Radio (Very High Frequency) The main difference between these two options is in the range of frequencies that they use. VHF / UHF CRT MICRON UV-Dualband-Radiosender 136-174 MHz - 400-470 MHz, 13,8 VDC, DTMF, Dual Watch, TOT, Scan, Talk … Often when you see a 1/4 wave on a mount the SWR isn't that low as its not a … We are the online division of an authorized Motorola and Icom radio dealer based in Tennessee. MF, or medium frequency, ranges from 300kHz to 3MHz and is often used for AM radio broadcasts. This is due to AM radio stations broadcasting in the 0.525 to 1.705 MHz band resulting in wavelengths that are roughly 100 times longer than VHF and 300 times longer than UHF. However, many digital radios can be changed to analog mode making them able to transmit an analog signal . Zur Vergleichsliste hinzufügen. At work we did some pre-tuning for a customer of a batch of MidBand VHF antennas on MagMounts earlier this week. Lower frequencies with their longer wavelengths tend to travel longer distances in open spaces outside, curving with the distant horizon while higher frequencies, with their shorter wavelengths, tend to travel in straight lines and do not bend with the curvature of the earth. What is the difference between VHF and UHF? Likewise, FM radio broadcasts range from 88 to 108 MHz, almost reaching the VHF band. UHF vs VHF Radios. The UHF vs VHF two-way radio decision depends heavily on your requirements. VHF radio waves normally travel within line of sight along the Earth’s surface. Large construction projects, schools, large entertainment venues, hotels, retail stores, manufacturing facilities, hospitals, high rise buildings, casinos and anyone else primarily using their radios inside or inside/outside in urban areas would all be good candidates for UHF radios. Usually channels of UHF have a higher bandwidths than VHF, therefore, carries more information. One important characteristic of radio waves is the wavelength which is the distance between peaks on a wave: UHF television refers to the use of ultra high frequency radio to broadcast to your television set. VHF propagation is ‘line of sight’ in nature and so is restricted to shorter-range communications. VHF equipment operates between the frequencies of 30 MHz and 300 MHz. With Motorola UHF and VHF two-way radios in Philadelphia, your workforce can stay productive, efficient, and always have the connection they need to get the job done. UHF antennas are smaller than VHF antennas as their wavelength are smaller than VHF, Filed Under: Communication Tagged With: 3G mobile networks, decimeter range, FM radio broadcast, GSM networks, radio frequency bands, SHF band, Television broadcast, UHF, UHF band, Ultra High Frequency, Very High Frequency, VHF, VHF band, wireless television broadcast. der UHF bereich geht etwa bei 400 MHZ los und ist das sogenante 70 cm band. UHF radios are much more popular overall than VHF radios in most applications where distance is not the primary need as they tend to be more versatile than VHF radios. VHF walkies operate on the frequencies between 136 and 174 MHz, they work over large distances with lower power consumption. 4. Signals at VHF and UHF … Our experts are here to guide you. December 03, 2014 No comments. nur das die fernsehfrequenzen in diesen bändern angesiedelt sind. VHF/UHF/HF. If your requirement is to cover large areas, VHF will be the better option but if the topography is urban then generally the UHF option is more suitable. VHF/UHF/HF. VHF und UHF sind lediglich nur 2 der bestehenden frequenzbänder z.b. Not just for off roaders, but for everyone and everything that uses wireless devices. Antenna. ... Rádios portáteis VHF/UHF Recursos adicionais 16 / 128 canais (VX-261/VX-264) When looking at your TV and the channels, the UHF channels will usually be numbered higher. VHF VHF refers to radio waves operating in the range of 30 to 300 megahertz with a shorter wavelength than high-frequency (HF) bands. VHF Definition What is the difference between VHF and UHF? UHF channels are typically given higher channel numbers, like the US arrangement with VHF channels 2 to 13, and UHF channels numbered 14 to 83. UHF television broadcasting is the use of ultra high frequency (UHF) radio for over-the-air transmission of television signals.UHF frequencies are used for both analog and digital television broadcasts. VHF band is sandwiched between HF (High Frequency) and UHF (Ultra High Frequency) bands in spectrum. UHF e VHF saiba a diferença. This means that since the waves are longer with VHF, it’s harder to disrupt the wave, therefore it travels further. GMRS The General Mobile Radio Service (GMRS) is a land-mobile FM UHF radio service designed for short-distance two-way communication. With Motorola UHF and VHF two-way radios in Philadelphia, your workforce can stay productive, efficient, and always have the connection they need to get the job done. The science behind VHF and UHF. Ham Radio, UHF, VHF, Cell Phones, and Emergency Dispatch Frequencies. One important characteristic of radio waves is the wavelength which is the distance between peaks on a wave: Wavelength is inversely proportional to the frequency. hat also mit rundfunk und fernsehen garnix zu tun. These VHF/UHF radios come in two varieties – one that look like toys, but are actually quite powerful. VHF radio is ideally suited for tactical communications. 2. I work for a company in the two-way Radio & accessory manufacturing area. UHF waves are mostly used for television broadcast and mobile phones. Difference Between Near Field Communication (NFC) and Bluetooth, Difference Between WCDMA and HSDPA Network Technology, Difference Between Coronavirus and Cold Symptoms, Difference Between Coronavirus and Influenza, Difference Between Coronavirus and Covid 19, Difference Between Giemsa Stain and Leishman Stain, Difference Between Molecular and Metallic Hydrogen, Difference Between Communicable and Non-Communicable Diseases, Difference Between Gravimetric and Titrimetric Analysis, Difference Between Orthoboric Acid and Metaboric Acid, Difference Between Regeneration and Fibrosis, Difference Between Culture and Media in Microbiology, Difference Between Oxirane Glycidyl and Epoxy Groups, Difference Between Filgrastim and Lenograstim. Television broadcast and FM radio broadcast (usually utilizes the 88MHz – 108MHz range) are two major uses of VHF. As a result, UHF will not travel as far in the outdoors. Both UHF and VHF radios are prone to line of sight factors, but VHF a little more so. However, VHF radio has weaker building penetration strength compared with UHF. Before we compare VHF radio vs CB radio, it is probably worth talking a … For example a 422 MHz receiver has an input stage and an oscillator that operate at UHF (422 MHz) but after those two stages the frequencies drop to intermediate frequency (IF) stages below 20 MHz and then to the audio stages. Because of that, there are a lot of VHF radios in existence compared to UHF. UHF vs. VHF Two-Way Radios VHF Radio (Very High Frequency) The main difference between these two options is in the range of frequencies that they use.