Two Way Radio 101 - Danger, Experts Made Here!
Ever find yourself staring at shelves of two-way radios, or hopelessly scrolling through web page after web page trying to make sense of it all? We’ve all been there. We created this article to provide insight into how radios operate allowing you better understanding of your current two-way radios. It will also help you to feel informed and empowered to make the best purchasing decision for any future two-way radios, putting an end to all that endless scrolling.
We will look at all sorts of two way radio topics:
- Frequency Bands
- Simplex, Conventional, and Trunked Two-Way Radio Systems
- Transmission Types
- FCC Licensing
- License-free radios
- LTE & Satellite Radios
- Radio Etiquette
This article will lay a solid foundation of knowledge for you, acting as a great resource to keep in your bookmark tab for future use. We’re all certified experts having read something only once, right?
Buckle up, partner, let’s get going!
Two Way Radio Frequency Bands
There are all kinds of frequencies in which different two-way radios can function.
“BUT WAIT!” You say. “I don’t even know what you mean by frequencies.”
Not to worry friends, let’s start with an intro into what a frequency is, and those of us who are coming into this with prior experience can feel free to skip ahead.
Think of frequencies as waves in a pool of water. We start with a still pool, in which there would be a frequency of 0 because the water is static.
Now imagine we give in to temptation and do a cannonball into the pool. Think about all the waves we will create as we disturb the water’s surface. Look at one spot in the pool and count how many waves pass by in 5 seconds. The number of waves you count in that time is the frequency.
See, Frequency is the number of waves that pass a fixed point in a unit of time. Using the image above, we can see a more uniform depiction of what the term frequency is describing. The unit of time being used in that image is 1 second. We can see that the frequency represented here is 2 Hertz or 2 Hz. Hertz is the unit used to measure frequency. A Hertz refers to the amount of time it takes a wave to complete one cycle, represented above.
The figure above gives a visual of frequencies at different wavelengths placed on top of each other. Wavelengths are defined as the distance between corresponding points of two consecutive waves; refer to the image below. The wavelength determines how many cycles are possible during a unit of time. The longer the wavelength the lower the frequency and therefore the shorter the wavelength the higher the frequency, depicted moving down the lines.
Now, the frequencies two-way radios utilize are much higher than our 2Hz example. We will need to think in terms of Kilo- (1,000’s) and Mega- (1,000,000’s) Hertz for the world of two-way radios.
Let’s say we are using a VHF, Very High Frequency, two-way radio system which operates in a 138 -174 Megahertz, or MHz, frequency band (or range). This means our system is sending out radio waves with a frequency of 138,000,000 – 174,000,000 Hertz per second. Crazy fast, and can you believe this is one of the lower ranges for frequency bands that two-way radios utilize?
Modern two-way radios operate using frequency bands from 134MHz up to around 900Mhz. The two-way radio systems we will look at today will be using frequency bands labeled:
- Very High Frequency (VHF) ~ 138-174 MHz
- Ultra High Frequency (UHF) ~ 400-512 MHz
- 800MHz ~ 806-824 MHz & 850-869 MHz
- 900MHz ~ 896-901 & 935-940 MHz
Why the variety of bands operating across such a large range of frequencies? The simple answer is lower and higher frequencies allow radios to be more specialized for different applications.
Remember how lower frequencies have longer wavelengths? This allows radios using lower frequencies to be more suitable for outdoor use over greater distances because the longer wavelengths will bend with the horizon. The lower frequencies are great for farmers, hunters, hikers, park rangers, etc., but they come at a cost of not performing as well in more urban settings. Longer wavelengths do not have much penetrating power, allowing them to bounce off the atmosphere and bend around the horizon, but this means they won’t go through dense materials like those in walls.
A radio wave with a higher frequency can more effectively go through walls and is very useful in urban settings, but the shorter wavelengths make it less useful over large distances. This is because the shorter wavelengths will penetrate straight through the atmosphere and continue in a straight fashion.
A great real-world example of this is when we consider AM vs FM radio. AM radio stations can be broadcasted clearly over hundreds of miles while we start to hear static from FM radio stations after getting about 30 – 40 miles away from the station. This is because AM radio is broadcast over a frequency band of 0.525 – 1.705 MHz, with longer wavelengths able to better bend with the horizon (figure above), while FM uses a broadcast range from 88 – 108 MHz. FM radio uses the higher frequencies to navigate the more urban environments it is usually broadcast from more smoothly, but won’t keep a clear signal for as far.
Very High Frequency (VHF) Radios
VHF radios operate within the frequency band of 138 – 174 MHz
Why use VHF Radios?
Radios that use this frequency band work best in open, flat terrain. As you might remember, radios with lower frequencies provide you with a better ability to communicate over long distances. Think back to the AM radio example. The longer wavelengths of a lower frequency radio allow your signal to bend over the horizon to reach your team member miles and miles away.
Who uses VHF Radios?
VHF radios are used at large by the recreational outdoor community and by public safety commissions, especially in rural counties.
I’m a surveyor looking to stay in contact with HQ while I am out conducting research about the landscape. A VHF radio is ideal for me because it allows me to cover great distances while knowing I will be able to stay in contact with my colleagues for both data communication and safety.
Are there drawbacks to VHF Radios?
While VHF two-way radios are great for rural use, dense foliage in thick forests and dramatic landscapes can still cause interference, or static, with your signal. Those long wavelengths just don’t like it when things get in their way. A clear line of sight is a big factor for the success of your VHF two-way radio system.
Likewise, if you are in the middle of downtown Chicago attempting to reach your friend who is working in a high-rise, you may experience some interference with your signal. This static is caused by the lack of signal strength as it attempts to penetrate through the many buildings. It could also be due to signal interference by other two-way radio communications since the longer wavelengths are more easily affected.
Ultra High Frequency (UHF) Radios
UHF radios utilize a frequency band of 400 – 512 MHz
This frequency band is by far the most popular choice amongst two-way radio users.
Why use UHF Radios?
People will generally go with UHF radios for indoor use or for when there are obstacles between users. Unlike radios employing VHF, those that use the UHF frequency band are perfect for use in a downtown setting like Chicago. The shorter wavelengths give these radios the power to get your message to your team member with ease. The concrete, glass, and other signal sources bear no match to the penetrating power of a UHF radio system.
Who uses UHF Radios?
UHF radios are ideal for professionals working in areas with densely packed buildings. Think about your security details in buildings or special events, hotel staff, and taxi services navigating the urban environment.
You are a House Manager for a production playing in New York City. You need to have open communication with your assistants and other staff to assure the convenience and safety of all audience members. You would be best served by a UHF radio system as it can navigate the environment you have with ease.
Are there drawbacks to UHF Radios?
As with VHF radios, the drawbacks of two-way radios using the UHF spectrum really come into play when you try to use it for a scenario it isn’t designed for. The distances involved in outdoor recreation play to the weaknesses of a UHF system. Unless, of course, you are out surveying rainforests or mountainous terrain and need the strength of the UHF’s shorter wavelengths to get through the canopy or rock formations.
Keep the wavelengths examples in mind. The shorter wavelengths for the higher frequency UHF system will shoot right through the atmosphere, given enough power, meaning it will not bend around the horizon. Think back to the image of the AM/FM/TV waves just above, with the higher frequency, FM, signals continuing through that atmosphere while the AM signal bounced back down to the surface.
Admittedly your typical UHF two-way radio system won’t have the power to actually send a signal straight through the atmosphere. Instead it’ll simply dissipate. Those examples still provide a good visual to keep in mind even though signal dissipation most often occurs when a signal is being reflected over too many surfaces without the power to continue.
800 & 900 MHz Two-Way Radios
These systems use frequency bands of 800 MHz - 806 – 824 MHz & 851 – 869 MHz and 900 MHz - 896-901 & 935-940 MHz
Who uses 800 & 900 MHz Radios?
These frequency bands are primarily for use by public safety services like police officers, firefighters, and emergency medical technicians, but there are some commercial wireless carriers and private radio systems utilizing them as well.
For instance, manufacturing, utility, land transportation, and petrochemical companies all make use of the 900 MHz frequency band.
Many of these organizations utilize a trunked radio system because of their many devices and interdependence needs. More details about trunked radio systems to come, but the picture below will give you a simple visual of a trunked system.
Why use 800 & 900 MHz Radios?
A trunked system with such strong frequencies pairs the great penetration power of high frequencies with the control of having control centers navigate the communication paths. Coming in handy for the primarily urban areas these are most utilized.
Are there drawbacks to 800 & 900 MHz radios?
Since the frequency is so high, these systems are very dependent on strategically placed antennas to allow for the large distances needed covering to be communicated over effectively. It is the same problem we face with UHF bands, with more power involved.
Most two-way radios operating in these bands require license agreements. Though 1 license-free option is the DTR700 by Motorola because of its low power usage, at 1-Watt. It is great for retail stores or small businesses in a tightly packed environment.
We have a great article going into more detail about the benefits of different frequency bands here. The article also goes a bit more in-depth about why one should choose a VHF or a UHF two-way radio system.
Simplex, Conventional & Trunked Two-Way Radio Systems
Your two-way radio system can use a few different methods of transmitting signals based on its programming. We will look at each in order of growing complexity. This section can be a bit dense, so frequent water breaks are recommended.
Simplex Radio to Radio Systems
Simplex systems use a single channel to transmit and receive information. These systems are strictly radio to radio using no repeaters for a signal boost.
- Radio to radio using analog transmissions.
- Does not use high powered repeaters, or in-between, radio systems.
- Any analog or digital radios support this.
- Radio to radio using digital transmissions.
- Does not use high powered repeaters, or in-between, radio systems.
- Any digital radios support this.
- All components (radios and repeaters) must use the same digital technology to operate.
- DMR - for Motorola
- NXDN - for Icom and Kenwood.
Conventional systems will utilize repeaters for boosting your signal. These systems have channels available for the user to select, as well as instant channel access.
- Radio to Repeater to Radio using analog transmissions.
- Uses a high powered repeater to boost the signal.
- Any analog dealer programmable radio (non-FRS) can be programmed to support this transmission method.
- Radio to Repeater to Radio using Digital transmissions.
- Uses a high powered repeater to boost the signal.
- Any digital radios can be programmed to support this.
IP Site Connect
- Radio to Repeater to Radio using digital transmissions.
- This technology can link multiple repeaters together via the internet (IP), which creates a system of repeaters all transmitting the transmissions at the same time. This creates a larger network of "conventional" repeaters for companies that want to connect multiple locations with common communications.
- You can connect up to 15 repeaters at 15 different sites using this technology.
- The Motorola XPR 3000 series, XPR 7000 series, SL 3500e, SL 7000 series, and XPR 5000 series mobiles support this technology
Trunked systems are when your communication is being transmitted from your radio to a control station which then chooses where your transmission will end up and on which frequency. These systems utilize a “pool” of frequencies that the control station can send communications over.
Capacity Plus Trunking
- Radio to Repeater to Radio using digital transmissions.
- This technology creates “pools” of available channels where users are dynamically allocated based on what's currently available. It is available in single-site operation or linked-capacity-plus, which acts like IP site connect.
- This technology is recommended for large plants or users with similar needs.
- You can add up to 120 repeaters at 15 different sites supporting up to 1,600 radios/site or 24,000 radios total.
- The Motorola XPR 3000 series, XPR 7000 series, SL 3500e, SL 7000 series, and XPR 5000 series mobiles all support this technology
Capacity Max Trunking
- Radio to Repeater to Radio using digital transmissions.
- This technology also creates “pools” of available channels where users are dynamically allocated based on what's currently available. Different from capacity plus trunking, in these systems, if all available channels are full, users will be added to a queue.
- This technology is recommended for extremely large operations. You can add up to 5,250 repeaters at 250 different sites supporting up to 3,000 radios/site or 90,000 radios total. This is the most complex level of two way radio systems available.
- The Motorola XPR 7000 series, SL 7000 series, and XPR 5000 series support this technology
Below, is an example of a trunked communication system. You can see how a variety of users are able to communicate. None of them are directly transmitting to each other (radio-to-radio); all communications are going through the antenna to the control computer and then redirected out into the field based on the need.
A couple other things to keep in mind:
- None of the methods discussed are band-specific, meaning you can program almost any frequency band to use either simplex, conventional, or trunked transmission methods.
- All repeater systems TX (transmit) and RX (receive) on different frequencies. Normally, for the UHF band this offset is 5 MHz, but for VHF it can be more or less than that.
Two-Way Radio Transmission Types
For over a century analog signals ruled the radio world, but the advancement of technology is once again changing things and radio is not immune to the digitization of the modern world. Even though most businesses and users still use analog systems today, the shift to digital systems is coming. A big driving force of this is the analog technology has hit a ceiling with innovations and people are still finding new needs in this ever-changing world.
Here you will see a brief breakdown of analog and digital systems, if you would like to know more about why making the move to digital could be beneficial, visit our article Analog V. Digital – 7 Key Differences to learn more.
Analog transmissions have been available for businesses since 1933 and used by the military for 20 years before that. As the name suggests, analog systems keep your voice as a wave while it travels to the receiver.
Most analog radios today utilize frequency modulation, or FM, producing a continuous wave with the voice signal. Advancements like FM have greatly reduced the cost and made analog systems very user friendly over its long tenure.
Benefits of Analog Radios
- Due to the longer time analog has been around, there are a great many accessories and add-ons available to analog systems. However, look for this to change in the near future as many manufacturers are discontinuing their analog production altogether.
- The "bleed off zone". While digital radios have ~25% better range (re analog vs digital article), once they hit max range the transmissions just stop. Much like an HD radio in a car. Meanwhile, analog radios can peter off slowly, which results in static but may eke out a little more range under specific situations.
- Analog systems use the natural voice since the signal is kept as a wave between receivers, something many users prefer
Disadvantages of Analog Radios
The newcomer on the scene, digital systems are still coming of age but are rapidly gaining ground on analog’s stronghold in the radio community. This is in large part because digital systems began at the peak of analog technology and provide the potential for innovations far beyond analog capabilities.
Benefits of Digital Radios
- Innovation – The main benefit to using a digital system is how it enables you to seamlessly enhance your systems as new innovations hit the market
- Digitization of voice – because a digital radio immediately translates your voice into simply computer language ( 0’s and 1’s ), you can better utilize your maximum range of the radio as well as better voice clarity between users by minimizing external background noise
- Conversation capacity – digital systems offer more paths of simultaneous communication as well as the ability to add unit ID’s and enhanced text message into a single channel
- Battery Life – the digital system offers ~ 40% more battery life than analog radios
- Backwards compatibility – Most digital systems come standard with the ability to communicate with your established analog devices by using select analog channels.
Disadvantages of Digital Radios
- Cost – currently digital radios do cost the consumer more, but as with analog radios, you should look for this price to drop dramatically as more innovations come into the market
- Learning curve – due to the software and enhanced functionality, digital systems can come with a learning period that some first-time users may find off-putting
- Quality of Sound - some users that have been using analog radios for a while might not like the "tinny" nature of digital transmissions. Although this can be offset on some high-end radios by adjusting the audio profiles.
Digital Schools of thought
With airwave congestion from the ever-growing two-way radio consumer market, the FCC and other legislative bodies have had to put regulations in place to protect the future growth of the industry as well as the security of communications.
The rise of digital radio systems has provided pathways for companies to lessen the amount of bandwidth needed per channel. In essence, the digital system can split the amount of bandwidth used in half through various technological advancements.
DMR – Digital Mobile Radio
Motorola utilizes this technology as their digital standard
This standard was created by the European Telecommunications Standards Institute (ETSI), that uses a technology called Time Division Multiple Access (TDMA).
TDMA takes your total bandwidth, 12.5KHz, and splits it up into two alternating time slots with each slot acting as a separate communication pathway.
This technology allows for fewer frequencies needed for the licensee
NXDN – Next Generation Digital Narrowband
This technology was developed by the companies ICOM and Kenwood. It utilizes Frequency Division Multiple Access (FDMA).
FDMA doubles your bandwidth capability like TDMA when compared to an analog system but does so by separating the conversations by frequency instead of using time slots.
You must remember that the two standards, DMR and NXDN, will not communicate with each other. Meaning, if you have a fleet of Motorola radios using DMR to communicate, you cannot add ICOM or Kenwood radios and expect them to integrate into your system seamlessly. In that instance you would need to decide whether to add more Motorola radios, or swap out your entire fleet, to meet your needs.
Before 2013, everybody was using systems that operated with a bandwidth of 25KHz. This was far too large when factoring in the growing number of users vying for space in the radio spectrum, every day.
The congestion caused by the large bandwidth is why the FCC mandated that all existing and future licensees implement equipment able to operate on bandwidths of 12.5KHz by Jan. 1, 2013, with the eventual goal of getting the bandwidth size down to 6.25KHz.
It’s this goal of reaching the 6.25KHz bandwidth that drove the innovations of TDMA and FDMA technologies because you are unable to transmit the voice as a wave through such a small bandwidth. Digitization for the win!
To visualize narrowbanding, think about a group of people standing shoulder to shoulder between two walls. As they are, there is no more space to fit anyone else. Now everyone turns to face one direction, creating space, or slots, between each person for someone else to occupy. This is a basic description of what the move to narrowbanding accomplishes.
The figure above shows how many more channels become available by the move to smaller and smaller bandwidths. At 6.25KHz, we have quadrupled the number of channels available for the radio community at every frequency.
The Federal Communications Commission, or FCC, is responsible for regulating the electromagnetic spectrum used by commercial and private users. They oversee optimizing the use of the spectrum for fair competition as the revolution in communication continues.
Many personal radio users will find they can operate without specific licenses granted by the FCC, but it is always good to know what is available for you as your needs may change.
General Licensing Info
- License agreements given out by the FCC will last for 10 years
- You can renew your license up to 90 days or less of your agreement expiring, and are granted a two-year grace period for renewal after your license expires
- Fees for licenses vary based on a number of factors. Here are a few things that go into calculating the cost of a new or revised FCC license.
- Type of license applied for, such as:
- Coordinated, license centered on set locations. More expensive
- Itinerant, license based on large areas of usage, usually nationwide. Cheaper than coordinated licenses, but more apt to interference from other itinerant users as the frequency pool is small and shared via all itinerant licensees
- Power Output, higher power generally = higher costs
- Transmission Type, analog or digital
- Advanced trunking systems
- Area of impact (mainly concerns coordinated licenses)
- An example of a higher license fee would be if you are at a high elevation in an urban area and want to put in a high powered repeater system. Your radio coverage would travel very far, which would need to be accounted for.
- Be aware that some license agreements have an age requirement of 18 years or older
If you'd like to learn more specifics about the process of obtaining an FCC license for GMRS or LMR radios, click here. In our FCC licensing article we go over reasons why you would need one type of license over the other, we explain the process of acquiring each license type, and go over some FAQ's about licensing.
Another great resource for your licensing questions is fcc.gov under the mobility division of the Wireless Telecommunication Bureau. There you’ll find detailed breakdowns of all their licensing scenarios.
Admittedly, the FCC’s site is pretty dense so I'd recommend trying out our FCC Licensing article or calling one of our Motorola Master Certified radio consultants at (888) 733-7681 who would be happy to answer any questions, first before getting bogged down on the FCC's official site..
With that in mind, let’s take a moment for a quick overview of some licensing scenarios put forth by the FCC.
Family Radio Systems (FRS) vs General Mobile Radio Service (GMRS) vs Land Mobile Radio (LMR)
Family Radio Systems (FRS)
As defined by the FCC, the Family Radio Service (FRS) is a private, two-way, short-distance voice and data communications service for facilitating family and group activities.
Most FRS radio devices are the type you find on the shelves of stores like Walmart, Best Buy, and sporting good locations. These make up the majority of the amateur consumer market for two-way radios.
The FCC has designated 22 channels for FRS use within the 462 – 467 MHz range it shares with GMRS.
Since you share the small frequency range with all FRS users, there's a good chance you'll find yourself in a situation hearing others conversations. If so, be respectful, change the channel.
Products in this category are “licensed by rule”, meaning a user does not need a license so long they are operating within the rules laid out by the FCC.
One of these rules is a 2-watt power limit for devices using the FRS, if your device exceeds this limit you will have to inquire about receiving a licensing agreement before use.
An FRS user is not permitted use of a repeater, or antenna, to further the range of their devices.
General Mobile Radio Systems (GMRS)
The FCC defines GMRS as a licensed radio service that uses channels between 462 MHz and 467 MHz. The most common use of GMRS channels is for short-distance, two-way voice communications using hand-held radios, mobile radios, and repeater systems.
GMRS operates under the same 462 – 467 MHz frequency band as FRS
These systems are mainly licensed out to individuals who need to use radio systems which exceed the 2-watt power limit put on FRS devices, but there are some cases where small businesses may utilize GMRS as well.
You must be 18 years of age to apply for a GMRS license agreement.
If you obtain a GMRS license, family members and those in your company can operate the GMRS stations and units within your license agreement regardless of age.
Your license agreement lasts for 10 years.
GMRS license agreements allow users to implement repeaters and stations to further their communication capabilities.
Land Mobile Radio (LMR)
Note: This is the class of two way radio sold by RadioDepot
LMR services are generally much higher quality and more complex than its GMRS and FRS counterparts. Public land mobile radio systems are to be used exclusively by public safety organizations (i.e. police, fire, and ambulance services), and use designated special frequencies reserved for the public safety sector by the FCC. Private land mobile radio systems are designed for private commercial use and are utilized by businesses ranging from high-rise hotels land surveying companies.
Devices in the LMR sector are all superior quality, rugged by design, and have high output power wattages. Making them ideal for the industrial and business sector.
LMR has been granted several frequency bands within which they can operate:
- 30-50 MHz (Low VHF Band)
- 150-172 MHz (High VHF Band)
- 450-470 MHz (UHF Band)
- 800 & 900 MHz bands (UHF)
As with GMRS, you are required to obtain a license from the FCC to legally operate your LMR device in any of the above mentioned frequency bands.
You will need to apply for your LMR FCC frequency license by making use of a frequency coordinator so both yours and everyone else's communication networks will all work smoothly.
- When buying a radio from us, we will help you in this process. We have relationships with frequency coordinators to make everything go smoothly
Your LMR Frequency License will be valid for 10 years
When applying for license, you will have to declare the rough quantity of devices, use of repeaters and any other network altering devices you plan to use. While this may seem tedious, it will allow your frequencies to be laid out the best for you and allow for any device you have programmed to the frequencies to be used freely.
For more details on the differences between the FRS, GMRS, and LMR sectors take a look at FRS vs GMRS vs LMR.
Itinerant vs Coordinated Licenses
These licenses are for people who need their license agreements to travel with them. Think about an independent contractor working on multiple job sites throughout counties or even different states. Itinerant licenses provide you the ability of not having to reapply for license agreements for each location you work in.
The FCC has set aside a list of frequencies for use by all itinerant licensees. This does mean there is a higher risk of communication interference due to the volume of users over the same frequencies.
The FCC requires Part 90 licensing for a defined band of radio products called Public Land Mobile Radio Services (PLMR). Types of radio devices typically requiring Part 90 certification are public safety radios (EMT, fire, police, etc.), paging devices, commercial radio systems, and radio location devices.
Coordinated licenses are for individuals or organizations looking to operate within the FCC’s business/industrial pool of frequencies under Part 90 certification. Such entities are required to obtain a radio station license for their frequencies.
A frequency coordinator, private organizations certified by the FCC, is needed to recommend the most appropriate frequencies for your needs.
Many people and companies choose to use radio licensing agencies to simplify this process. For instance, Radio Depot can help you secure a license without ever having to communicate directly with the FCC or a coordinator.
Applicants for these licenses must show proof of frequency coordination to be considered. This process is to ensure the efficiency of the PLMR spectrum for the benefit of the public.
License-Free Two-Way Radios
Many of you will find you won’t have any need for products that require FCC licensing. Here is a list of some radios that can operate license-free, along with some details of each, giving you a sense of what’s available without having to apply for a license agreement. For more information on any of the products listed, click the link attached.
DTR700 by Motorola
- Use digital transmission
- Ideal for schools, hospitality services, retail, and churches
- Has 50 channels in the 900MHz frequency band
- Max power output = 1-Watt
NX-P500 by Kenwood
PKT-23 by Kenwood
TK-3230DX by Kenwood
VL50 by Motorola
Each of these models is great for small-scale use. They have their own unique benefits better suiting them for individual cases. If interested, be sure to research their specifics or ask one of our certified consultants to help guide you.
As always, we want you to be the most prepared when considering buying any product.
LTE & Satellite Two-Way Radios
LTE and satellite radio technologies make up a significantly smaller portion of the radio markets today than Land Mobile Radios (LMR), but each has unique characteristics making them good to have some knowledge about.
LTE, standing for Long Term Evolution, is a trademark owned by the European Telecommunications Standards Institute (ETSI) and is an open standard for digital cellular technology. This technology has been developed for very high capacity data transfer with very low latency over networks. Your modern cell phone makes use of the LTE network every day.
The biggest difference in LTE radios over regular LMR systems we have talked about is how they transmit information.
LTE uses data transmission. These radios convert your voice into data packets which are then re-assembled as audio voice on the receiving end. This is ideal for the market that is transitioning to smaller and smaller bandwidth usage (6.25KHz).
The impressive data performance LTE systems offer could mean they become more standard in even the near future, but presently they have some serious drawbacks keeping them from popularity. The image below will give you an idea of how an LTE system transmits your data. Notice how everything is being relayed through the cell tower.
LTE Radio Drawbacks
- The most significant pitfall of LTE radio systems today is due to the incredibly small cell size they use for transmitting your data.
- The small data cells require significantly more towers for transmitting than your typical LMR systems. This will inherently create very high costs.
- Your data performance also greatly decreases as you move further away from a tower.
- The LTE coverage is bandwidth sensitive relying on the network to load at any time. Meaning your transmission could be greatly affected near your coverage boundary, and in heavy traffic scenarios, could fail altogether
Satellite radios are great for applications where your communications need to be covered over vast distances, in remote locations, or in extreme terrain.
This technology utilizes transmission via satellite link to connect radio users, making it possible for communication in instances where traditional LMR systems will fall short.
The above figure gives a simple illustration of how satellite communication is done. Two antennas facing the satellite can relay information to each other.
There are a few different types of satellites that you can utilize for satellite radio communication.
- Geosynchronous Orbit (GEO)
- High Earth orbit, ~ 22,236 miles or 35,786 km, with speed matching the earth’s rotational velocity so it appears to be at a fixed point in the sky.
- Provide unrivaled communications coverage with only 3 or 4 needed to be able to cover virtually the entire globe
- Middle Earth Orbit (MEO)
- Orbit altitude ~ 1,243 miles (2,000 km) up to the high earth orbit
- Travel at their own speeds requiring automatic tracking by dishes or having to wait for the next available satellite to pass by
- Low Earth Orbit (LEO)
- Orbit altitude ~ 112 miles (180 km) up to the medium earth orbit
- Also travel at their own speeds requiring automatic tracking by dishes or having to wait for the next available satellite to pass by.
There are also a few different methods of communicating with the orbiting satellites available.
- The U.S. based company Iridium offers a system that incorporates brief-case sized portable battery-powered terminals which you can plug into for satellite link. You only need to point the receiver in the general direction of the satellite to obtain a link. The links these systems give are rather slow, not supporting broadband but are good for simple tasks like two-way communication.
- There are also VSAT (very small aperture terminals) satellite communications systems which are two-way ground stations set up with an antenna. These systems can point to or track a particular satellite. VSATs not only can be stationary but can be attached to a vehicle due to their small size and can be disassembled and re-located quickly. These systems also support much higher data rates allowing for more complex tasks.
Drawbacks of Satellite Radios
- Satellite radio communication can become costly very quickly, not only because of the advanced instruments you must use, but also due to the data rate pricing model for transmission. With both Iridium and VSAT systems, you pay a flat rate by-the-minute or by-megabyte which can be very expensive when compared to options here on Earth.
- For satellite up/downlink to work your antenna must be in true line-of-site with the satellite. Many instances that can throw your connection off include being in a forest with a dense canopy, at the bottom of a ravine, or on rough seas. Even accidentally knocking into your antenna can disconnect you from your satellite link.
- Another possible downside is the time it takes for your signal to travel the distance between the ground, the satellite, and back down to Earth. This means your system will experience latencies of typically up to a half-second for GEO’s and only a little less for MEO and LEO’s. That half-second doesn’t sound like too much but can mean you are not able to communicate or control remote machinery in real-time.
- Lastly, your system is vulnerable to the single-point-of-failure in your satellite. This can be due to mechanical errors, the growing amount of debris in orbit around the planet, or solar flares. Also, MEO and LEO satellites are vulnerable to atmospheric drag causing eventual loss of altitude.
Two-Way Radio Etiquette
Acquiring your radio system is only the beginning of your radio career. There are communication techniques that will allow you to make the most of your conversations over the radio. You don’t want to spend all this money and end up not being able to get your point across, right?
Golden Rules of Radio Communication
- Clarity: Speak in a clear voice, usually a bit slower than normal speech. Always speak in a normal tone, never shouting.
- Simplicity: Keep your messages simple.
- Brevity: Keep your messages precise and to the point.
- Security: Never transmit confidential information over the radio unless you are absolutely certain your security systems are intact. Always keep in mind radio frequencies are shared with limited security lockouts, especially for analog transmissions.
Some more basic rules to know for radio transmission are:
- The accepted international radio language is English, except in some cases where you are specifically licensed to use another language.
- Think before you speak!
- Decide what you are going to say and who it is meant for
- Avoid abbreviations unless they are well understood by your group
- Wait your turn to speak. Radio frequencies only transmit one thing at a time, if you try to speak while another is speaking you will only miss that information.
- Do not respond if you are not sure the call is for you. Wait for the appropriate call sign before you respond
- Perform regular radio checks to ensure your system is in good condition
- Make a habit of returning your receivers to their charging bases to ensure your radios battery life
- Memorize call signs, locations, and radio stations people you communicate with regularly, use.
- Wait a few seconds between “handoffs” to allow for others to break into the conversation
- After pressing the PTT (push to talk) button, wait a moment before speaking to ensure your entire message is picked up by your radio.
Below is a sample conversation putting some of these conversation standards into use.
Alex : Mark, this is Alex. Over.
Mark : Alex, this is Mark, Stand By. Over.
Mark : Alex, this is Mark, Go Ahead. Over.
Alex : Mark, this is Alex, there is a car accident at mile marker 6 on Interstate 55. Over.
Mark : Alex, this is Mark, confirming the car accident at mile marker 6 on Interstate 55, emergency services will be notified. Over.
Alex : Mark, this is Alex, location confirmed, thanks for the help. Over and Out.
Notice the consistent use of each other’s names as well as closing each transmission with “over”. Radio users make use of a common language for clear communication.
- Go Ahead – Resume transmission
- Say Again – Re-transmit your message
- Stand-by – Transmission has been acknowledged, but I am unable to respond now.
- Roger – Message received and understood.
- Affirmative – Yes (avoid yup, nope, etc.)
- Negative – No
- Over – Transmission finished.
- Out – Communication is over, and the channel is available for others.
When talking over the radio you should make use of the Standard NATO Alphabet when spelling out words over the radio to ensure your message is received properly.
|A - Alpha||B - Bravo|
|C - Charlie||D - Delta|
|E - Echo||F - Foxtrot|
|G - Golf||H - Hotel|
|I - India||
J - Juliet
|K - Kilo||L - Lima|
|M - Mike||N - November|
|O - Oscar||P - Papa|
|Q - Quebec||R - Romeo|
|S - Sierra||T - Tango|
|U - Uniform||V - Victor|
|W - Whiskey||X - X-ray|
|Y - Yankee||Z - Zulu|
Well, it was a long journey, but we made it! This knowledge you’ve got isn’t only going to greatly prepare you for all your radio needs, but also let you show off to your friends while you talk about Geosynchronous satellite orbits and discuss wavelengths by the pool.
Do remember, that revisiting this information will always help to in-grain it further.
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