Created: 2024-08-17
Updated: 2025-10-31 – updated and added a 2nd page that compares all the LTE radios now on the market.

Why did I write this article? Well I kept getting asked questions about them (especially Rapid Radio who have been relentless in their advertising), like how they work and what’s different between them and apps like Zello. So I did some digging, ask them some questions, which they never replied to when I asked on Facebook where there ads are all over the place (I see them several times a day!). Of course they also took full advantage of the large scale AT&T outage and other disasters to promote that their radios will work when cell phones won’t. That last claim really got me investigating as I know a little bit about cell technology as I currently work on the IPAWS program.

A Little Technical Background

LTE is a standard of digital communications adopted by most countries and is used in cellular phones, or wireless data networks and was introduced in 2010. The specifications call for downlink peak rates of 300 Mbit/s, uplink peak rates of 75 Mbit/s and a transfer latency of less than 5 ms. This means it can handle fast-moving mobiles and supports multi-cast and broadcast streams.

Cell Towers

Cell towers are owned by both cell carriers and third-party companies, depending on the situation. Many cell carriers, like AT&T, Verizon, or T-Mobile, own some of their towers to maintain control over their network infrastructure. However, a significant portion of cell towers—often over 70% in the U.S.—are owned by third-party tower companies like American Tower, Crown Castle, or SBA Communications. These companies build and maintain towers and lease space on them to multiple carriers, which helps carriers reduce costs and expand coverage without the burden of owning and managing the infrastructure.

The leasing model is common because it’s cost-effective. Carriers rent space on a tower to place their antennas and equipment, often under long-term contracts. Third-party owners benefit from steady revenue by hosting multiple carriers on a single tower. In some cases, municipalities or private landowners also own towers and lease space, though this is less common.

The exact ownership mix varies by region and market, but the trend has shifted toward third-party ownership in recent decades due to the high costs of building and maintaining towers.

Frequencies

Cell towers send and receive different types of signals to make your phone work for calls, texts, internet, and other features. These signals are like different “channels” or pathways that carry specific kinds of information between the tower and your phone. Here’s a simple breakdown of the main types:

Control Channels These are like the “setup crew” that gets your phone connected to the network. They handle things like:
- Helping your phone find and join the network when you turn it on.
- Telling your phone when it’s time to send or receive data.
- Managing handoffs when you move between towers (like during a drive).
- Sending instructions to adjust your phone’s signal strength to save battery or improve connection.
Voice and Data Channels These carry the stuff you actually use your phone for:
- Voice: For phone calls (in modern networks, calls are sent as data packets, like an internet call).
- Data: For everything else—browsing the web, streaming videos, sending messages, or using apps. These channels are shared, so the tower decides when your phone gets to send or receive to avoid mix-ups.
Synchronization Signals These are like a clock and ID card for your phone. They help it:
- Sync up with the tower’s timing so signals don’t get jumbled.
- Figure out which tower it’s talking to (each tower has a unique ID).
- Check signal quality to keep the connection strong.
Broadcast and Paging Channels These are for messages sent to many phones at once or to get your attention:
- Broadcast: Sends info like emergency alerts (e.g., weather warnings or AMBER alerts) or network details (like what services are available).
- Paging: Wakes up your phone when you get a call or text while it’s idle (like when your screen is off to save battery).

How It All Works

Think of the tower as a busy traffic controller. It uses these channels to juggle calls, texts, and data for thousands of phones at once. Each channel has a specific job to keep everything running smoothly. In older networks (like 2G or 3G), voice and data used separate paths, but now (in 4G and 5G), it’s all sent as data over the same fast channels, with special priority for calls to keep them clear and quick. The signals travel as radio waves in specific frequency bands, and the tower makes sure they don’t interfere with each other.

Cell towers are also capable of “cellular broadcast.” This is a “one-to-many” one-way that goes to all cell phones in range at the same time. Unlike a text message there is no confirmation that a cell phone received the message. Think of it like a regular AM or FM radio station. This capability is what is used by the Integrated Public Alert and Warning System (IPAWS) where local authorities can send emergency messages, such as Amber alerts. The National Weather Service (NWS) also has the ability to send severe weather alerts, like tornado warnings, through IPAWS. Similar capabilities are used in other countries, in Canada it is called Alert Ready, Australia it is called Emergency Alert Australia and in the United Kingdom it is called the UK Emergency Alert System (only introduced in 2023).

For a more in-depth article on cell towers read this article https://fortunefavorstheprepared.com/cell-sites-and-their-services/

Cellular Frequency Bands

Cellular frequencies are listed by band. For each band there is a set of designated uplink (repeater input) and downlink (repeater output) frequencies, permitted bandwidth and, just like ham repeaters, assigned pairs. The specific frequencies aren’t important for this article however I have listed the bands and the cellular providers that operate on those bands (some companies may have merged or only operate in specific markets). This will become apparent later in the article.

Band 2 1900 MHz AT&T
Band 5 850MHz AT&T Visible, Verizon, US Cellular, Mint Mobile, Cricket Wireless, Straight Talk, Ting, T-Mobile, Lycamobile
Band 12 700MHz AT&T, Cricket
Band 13 700MHZ Ting (GSM), Verizon
Band 17 700MHz AT&T, Cricket, Straight Talk, H20 Wireless
Band 14 700MHz FirstNet (managed by AT&T) for First Responders only
Band 66 1700/2100 MHz AT&T, Visible, Verizon, US Cellular, MetroPCS, Mint Mobile, Cricket Wireless, Ting (GSM), T-Mobile, Lycamobile

Zell o

Zello is a radio type application, with a push-to-talk button. You can connect one-to-one with someone or one-to-many in a group. You can create a group and password protect it, so you only let in people you want to. There is also a messaging application with the same one-to-one or one-to-many group.

Signal

Signal is another common app that is encrypted. It provides a messaging as well as a phone call capability. As with other similar apps you can create a group message.

Now or Later

IP apps like Zello or Signal may work when you can’t get a voice call. However, when using the radio or calling feature remember that you are demanding a “now” connection from the network. Whereas when sending a message the system can ‘stack’ them and send as bandwidth is available.

Push to Talk aka Radio over LTE

Radio over LTE (Long-Term Evolution) refers to push-to-talk (PTT) communication services that leverage LTE cellular networks to provide instant, two-way radio-like communication. Unlike traditional two-way radios that operate on dedicated frequencies (e.g., VHF, UHF), Radio over LTE uses 4G/5G cellular data networks to transmit voice and sometimes data, enabling wider coverage, higher audio quality, and additional features.

Key features include:

Push-to-Talk: Instant voice communication with a button press, similar to traditional walkie-talkies.
Broad Coverage: Utilizes existing cellular infrastructure, offering nationwide or global reach (depending on the provider) without the range limitations of traditional radios.
Advanced Features: Supports group calls, private calls, location tracking, text messaging, and integration with dispatch software, often accessible via dedicated devices or smartphone apps.
No Cell Service Fallback: Some devices offer simplex communication (e.g., on FRS frequencies) when cellular coverage is unavailable.
Carrier Aggregation: Higher LTE categories (e.g., Cat 6 and above) use carrier aggregation to combine multiple frequency bands for faster data rates, improving performance in congested areas.

Devices typically require a subscription for cellular data and access to the PTT platform, with costs varying by provider. The technology bridges traditional radio functionality with modern cellular capabilities, making it ideal for professional and critical communication needs.

Redundancy

All of the providers appear to have a SIM cards that are configured to work on all the cell networks. This means that when one provider is down, or their is no cell tower coverage, it will switch to another carrier. So the device has at least three levels of redundancy (if we assume AT&T, Verizon and T-Mobile as the core cell providers). This capability, or redundancy, is where LTE radio’s have an advantage over your cell phone, and apps like Zello and Signal.

However, in a major disaster where all cell towers have been destroyed or are not connecting to their network they will not work. Some radios do have VHF or UHF frequencies in them and will revert to those, but their range will then be limited by the frequency they are using and the terrain. Initial investigation appears show they may be using FRS frequencies (more information is under each specific brand below).