Comms At Blackline - Zello and UHF Working Together

Updated: May 27

“No Comms, No Bombs”


This statement underlines an important truth - without communication, it is very difficult to organize and complete an objective. In airsoft military simulations (milsims) and skirmish games, VHF/UHF Radios have been the standard. Low-cost options coming from Chinese companies like Baofeng and Puxing have made this tool accessible to almost everyone and allowed airsoft games to organize in a way that would otherwise be impossible. However, with dozens of radios coming online at an event and more complex scenarios taking place, the cracks in the system are starting to show.


The Challenges

The most visible problems that occur are frequency congestion and poor communications procedure.


In many countries, the radio frequencies are divided and managed by the government. For unlicensed users, the FRS/GMRS band of frequencies is the most accessible. This narrow set of 22 frequencies has worked well for small to mid-sized events with minimal command and control. However, when this scales up to 60+ players all looking to manage squad and command communications for two teams, available channels start to disappear.



Compounding the lack of available channels is poor training and a lack of high-quality accessories. The hot mic and comms stepping can be excessive and can effectively shut down entire frequencies.


An unfortunate side effect of these problems is that players will stray off the FRS/GMRS bands without authorization. What seems like an innocent and practical solution to busy frequencies can actually result in fines. An increase in these situations has recently resulted in a crackdown on the import of programmable VHF/UHF radios in Canada.


Blackline events add a few unique challenges to this list. Events may take place across multiple sites or cities that are hundreds of kilometres apart which makes UHF impractical. We also permit full frequency scanning so open communications are always at risk of being intercepted by SIGINT teams.


The Solutions

There are a few options and mitigation strategies offered up by airsoft and milsim events. They include heavy restrictions on who can use what frequencies, suggesting individuals become licensed amateur radio operators, purchasing high-quality radios and leasing frequencies, or renting equipment and towers from radio service providers. While all of these options are ‘good’, they come with a series of costs and restrictions.


First, amateur radio licenses mean your communications are public and can't be obscured with callsigns or codewords. Second, leasing a frequency in Canada means using radios that meet the Industry Canada certifications (Baofeng and Puxing do not). Third, renting radios and service from a provider here will cost about $50 per device and the range is still limited by the service area of the rental company. Finally, events or game hosts placing restrictions on who can use a radio and on what channel reduces realism and leaves a lot of people without communications. These challenges may not apply to every country or jurisdiction, but they do for us here in Ontario, Canada.


This is why Blackline Events started to use Zello.



Zello is a radio app for iOS and Android phones and is a provider of a service called 'PoC', 'PTToC', or 'Network Radio' communications. PoC and PTToC stand for 'Push to Talk over Cellular'. As long as cellular service is present, Zello can link together people anywhere in the world. In fact, Blackline has begun allowing remote observers that listen in on radio traffic from overseas (Rich at The Reptile House was one of our first). The free version allows anyone to create a private secure channel for their group. These features mean Zello immediately addresses a few of the challenges with VHF/UHF radios.


  • Security - a channel secured with a password can’t be accessed by unauthorized users. The paid ZelloWork version allows an admin to control users and passwords for an extra layer of security (We've deactivated users when they were captured by the enemy).

  • Kill Hot Mics - a setting can be adjusted that lets admins cut into a message after a certain amount of time. If a hot mic has started, you can kill it within seconds.

  • Limitless Channels - Without frequency limits, teams can create private channels for themselves, and have others connected to a command channel.

  • Range - Zello uses infrastructure that is constantly being improved and expanded. Cellular service is reaching even remote parts of the world and is backed by huge companies looking to improve their technology. Zello isn’t dependent on huge radio towers and small companies managing upgrades to UHF/VHF infrastructure.

  • Cost - Zello is free in its basic form, and this free option meets the needs of most events. Almost everyone already owns a cellphone, so the hardware cost is kept to a minimum. Some of the smallest, most useful accessories are inexpensive.


There are some additional benefits for people willing to pay for a ZelloWork account. This version of Zello can allow the administrator to create and delete user accounts, manage channel assignments, and adjust the various settings for channels. But there are two features that make this investment worth it.


First, all communications can be recorded. A full record of all communications and their metadata is stored on the ZelloWork servers. The ability to download and compile messages means all the radio traffic from an event can be shared to study what happened or to let others listen to the experience.


A full account of all command and control communications for Blackline Event 1905a



Second, all ZelloWork users can be location tracked. When the app is running, Zello will broadcast the location of the user back to the server. This means that the admin has almost real-time visibility to where personnel are. Live location tracking of participants has huge benefits for both strategic and safety applications.


Video clip of the TOC monitoring an insert using live location tracking at Blackline Event 1908c



Even with all this praise for Zello, there are still a few drawbacks to PoC, PTToC, and network radio technology. Primarily, cell service isn’t in every location and dead zones exist. If all you use is Zello, you may find areas where you’re denied communications. You'll also need a data plan. Zello uses very little data, but it's not zero. Second, the accessories for PTTs are still a bit rough around the edges. More and more companies are developing quality solutions but not every accessory is perfect. Finally, while dedicated 'network radio' devices exist, the costs may force people to rely on their phones. Not everyone is ready to take their expensive pocket computer into rural environments.



How Blackline Combines Radio and Zello

We recognized that VHF/UHF and Zello both have their share of benefits and deficits and neither one could solve all our communications problems on their own. As a result, we’re experimenting with a blended option that has seen positive results: We use Zello for command and control, and UHF for squad comms.



Command and Control

With the location tracking features and the wide-area communications capability, we use ZelloWork for our command and control functions. We stand up our tactical operations center anywhere in the world and connect to our players. This means we can see the location of all users for safety and strategic functions. While all users are connected to the ZelloWork channels, we primarily communicate with team leads or their designated comms person. This keeps the command and control functions targeted to those that need to hear it while leaving the rest of the participants free to take care of their assigned tasks.


It's important to note that our TOC setup does require a good internet connection. If the connection is too slow, Zello messages can come in with a bit of a delay. At sites where we didn't have access to a wifi network, we used to do this with a hotspot from a phone. Recently we've been experimenting with a wifi hotspot called the Skyroam Solis. We've had some positive and some negative experiences, but overall it meets our needs. For more details on how to set up a TOC, watch for a future blog post on the process.


Squad Communications

On the field, teams use an FRS/GMRS radio channel to communicate amongst themselves, but only when required. Since most team movements are within visual and voice range, we find that the amount of radio traffic is minimal. The radio channels are available if extended distance or noise discipline is required. The minimal use of these channels reduces the chance they’ll be monitored, and with strategic messages moved to Zello, the value of the intercepts is negligible.




The Communications PACE Plan

The split between Zello and UHF does require a more advanced approach to communications but the military forces of the world have already addressed this through the development of a PACE plan. An acronym for Primary, Alternate, Contingency, and Emergency, the PACE comms plan lays out the units involved in an operation and what channels can be used to contact them. All units receive multiple methods of communication in the event networks or equipment fail. (Wikipedia - PACE Communications)


Managing Information Flow

While the Tactical Operations Center (TOC) has many roles, one of the primary functions is managing information that flows between units. The TOC has several individuals who span across the Zello Channels and push important recon or situation updates from one team to another. These updates include location information. Monitoring a live map, the TOC can see if two friendly units are approaching each other and warn them of the contact. The TOC can take an active role in managing the meetup or pass off a UHF frequency to the teams allowing them to manage it themselves.



The Future

For Blackline, Zello and PoC / PTToC technology will continue to be a vital component of our operations. There are no inexpensive and accessible UHF solutions to our wide area communications needs or the other challenges we listed above. Whatever solution we offer has to be affordable for our players, and Zello fits that need nicely. Aside from that, Zello provides a lot of added benefits that turn a tactical operations center into a valuable tool.


Accessories are the next big hurdle, but as Zello continues to expand it's reach, more vendors are producing more reliable products to support it. It's challenging to find trustworthy products, but we've been collecting them in an article which might help you select the one right for your activities.


In the meantime, we'll continue to refine how we manage these tools, but it's safe to say a Zello and UHF blended solution will be part of all future Blackline Operations.



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