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Friday, November 02, 2018

Review: Retevis RT-51 Basic PoC Network Radio

A network radio or PTT Over Cellular (PoC) device changes the way traditional two way radio users think about reliable unlicensed and local/non-local communications.
"Network radios use existing cellular infrastructure just like your smartphone in order to communicate both near and far"
The most basic PoC radio such as the Retevis RT-51 reviewed later in this article has better coverage compared to a smartphone that uses the same network due to antenna placement and configuration.

This creates unique applications and disruptions for those interested in communication equipment not seen since the days of Nextel and its iDEN technology that created the first wide scale PTT/cellular service concept back in the 1990's.

Overview:  Competitive Landscape

To set a baseline comparison, lets first compare competing unlicensed FRS and MURS radio services in the United States along with two non-critical licensed radio services known as GMRS and Amateur Radio.

Our goal with this article and review is to inform non-critical communications users about the benefits of network radio solutions.

Comparing the physical characteristics of one vendors traditional
analog/digital VHF/UHF radio (RT-3) and its basic network radio (PoC) offering (RT-51)

Licensed versus Unlicensed Radio

In the United States, there are specific frequencies that can be used with no license.  Most of these are designed for consumer use and occasional business use of a non-critical nature. 

Family Radio Service (FRS) and Multi Use Radio Service (MURS) offer different benefits to its users looking either for local or mid range communication. 

FRS uses 14 channels in the 462 and 467 MHz range with a maximum power output of  500mW and no ability to use external antennas.  No more than $60 USD for a pair of basic FRS radio often needs to be spent and the most professional quality FRS radios with other features like weather broadcast reception often sell for less than $150/pair. Average realistic communication range is less than 2 miles.

Example FRS radio made by Retevis. FRS in the United States or PMR and other
 similar services in other countries offer clear local unlicensed voice communication

MURS in comparison to FRS has only 5 channels with up to 2 watts of transmitter power and the ability to use external antennas for greater range.  There are some business users who still use these channels that at one point were called "green dot", "blue dot", "red dot", etc itinerant channels before MURS was an official service in the United States less than 10 years ago.

For a dedicated MURS only radio, pricing would be $150 to $400 for a pair of them. Average realistic communication range is about the same as FRS, but will tend work for greater distances in unobstructed residential environments or more reliably outdoors.

A MURS radio tends to be more expensive compared to FRS radios and there are fewer consumer grade options available for purchase which keeps MURS as a "best kept secret" for reliable mid range unlicensed communications.

Motorola offers its model RDM2020 and RDM2025 as
MURS only radios available for consumer purchase

With either the FRS or MURS service, communications is often limited to less than 3-5 miles.  There is no legal way to increase the range of these services with repeaters. General Mobile Radio Service (GMRS) does however offer this capability however for extended communication range.

Important: There are very few "legal" radios that combine both the VHF MURS and UHF FRS/GMRS functions into one radio.  There are many capable radios to do this however.

GMRS is unique as a licensed service that shares a few overlapping channels with FRS for some level of licensed/unlicensed interoperability.

Basic combinations of GMRS and FRS radios can usually be purchased for less than $100/pair and the advanced repeater capable radios selling for not much more.

Standard FRS radios are advertised as 14 channel models and the FRS/GMRS versions are 22 channel, not including the input frequencies for repeater GMRS operation.


Business users such as property management companies, construction, maintenance and other non-critical communication users have little choice but to turn to specifically licensed frequencies should they require greater coverage range or privacy. 

Pricing for licensing varies along with equipment maintenance and compliance costs. A general overview of licensing costs can be found here.
GMRS is typically not the best for business use because other unlicensed users may interfere with important business communications.
Citizens Band (CB) at 27MHz is mentioned only in passing within this overview of unlicensed radio services due to different characteristics too dissimilar in operation and equipment compared to FRS, MURS, GMRS and amateur radio.

Amateur radio is a licensed non-commercial communications tool that offers the benefit of all the characteristic benefits of different frequencies and spectrum plus the ability for larger antennas and higher power.
A basic amateur license in the United States is known as the Technician Class and permits the use on any frequency for any type of communication above 28.3 MHz and limited data only communication below. 
Gaining a license to become an amateur radio operator is very easy and there are very affordable radios that can be used on part or all of the most common spectrum in use with its 700,000 users in the United States.


Selection of modern amateur radios that offer different combinations of spectrum and communication modes.
MSRP range from $150 to $500 for those pictured.

Amateur radio also offers true "radio to radio" capability, communication through repeaters for extended range when using inexpensive hand held radios and also decentralized networks such as Brandmeister for a mix of local and global communication capability, like that offered by a  network radio.

This is without mentioning long range HF 1.8 to 30 MHz communication which most people associate with amateur radio which often leaves out the VHF and UHF offerings including 144-148 MHz, 220-225 MHz, 420-450 MHz and even 1.2 GHz!

Here is a comparison chart between the different services and spectrum the services covered in the article can be found.


Retevis RT-51 Network Radio Review

The Retevis RT-51 is very well built and feels like its capable to stand up to daily use in bad weather.

The manufacturer lists its IP67 rating for moisture and dust resistance as part of its features which also include loud volume, easy to push buttons and a simple menu system to access key features.

A full color display shows the incoming caller name to help identify who is speaking.  Time, date, battery life and network signal strength also appear and is easy to read in most lighting conditions.

The RT-51 can also announce various operational parameters for the visually impaired in situations where looking at the display is not possible.

The Retevis RT-51 and the TYT IP-350 are identical radios.
The major difference with Retevis is more responsive
customer service and possibly warranty support.

Operation of the radio is very easy with a power and volume function built in to one of the top mount controls.
The knob between the volume and antenna allows the user to select between different groups, explained later in this review.
At a price of less than $150 each, the Retevis RT-51 is unique in that it is a high quality product for a moderate price similar to that of its line of equipment marketed towards amateur and commercial radio users, such as its VHF and UHF only radios along with dual band versions.

Retevis offers the least expensive and basic network radio (PoC). 
Competing and more complex network radios  can cost more than $500 each.

Many manufacturers today offer digital communication capability such as DMR which has been adopted as the replacement for aging analog only radios. Benefits of DMR include user identification, location tracking, flexible group or private calling and management of users through special programming and console software.

RT-51 Experience: Out Of The Box

It is not possible to buy one, two, five or one hundred  of these radios and use them without first having two critical items.

Critical Item #1:   Each radio requires an inexpensive cellular prepaid or post paid data plan that will work on compatible mobile networks such as AT&T and T-Mobile.

A SIM card will need to be installed in each radio so it can work. No "radio to radio" calling feature is possible without a network based data plan with the Retevis RT-51. The spectrum that the Retevis uses is licensed to the mobile carrier networks such as those found at 800 and 900 MHz plus  1.7 GHz, 1.8 GHz 2.1 GHz and 2.6 GHz. There is no 2.4 GHz Wi-Fi of 2.3 GHz amateur spectrum accessible in the RT-51's ZTE 3630 4G LTE modem

The great news is that even with the least expensive $7.99/month plan on offer from FreedomPOP which offers 2 GB per month, the radio will likely only use 25% of that bandwidth even with heavy use. For users looking for many radios, it could be possible to pay even less per month per radio on a data plan.

No matter where a user is the radio will work just as long as there is network coverage available. This translates to 95% or better percent reliability in most any area that network operators cover.  This is a major benefit of a network radio compared to traditional radio. Plus, there is no need to invest in infrastructure, such as a repeater.

Underside of RT-51 showing the
removable door and SIM card slot

Critical Item #2
:

Once the radio has a data plan and SIM card - the radio needs to communicate to a server that routes communication between users.



Retevis offers two different options to make operation of the RT-51 easy.  For $10 a year, Retevis can host the PTT Smart Dispatch software on a US based server.

All that needs to be done is share the user ID for each user with Retevis and let them know how to set up groups for your users.

Easy menu navigation allows selection of
Group, Member, Friend, Recording, GPS, Setup

Each user can contact each other by "private call" or all users assigned to specific groups.  This "hands off" option is best for users who do not need to track user locations from a central dashboard.
  • Group:  Allows a user to contact any member that is assigned to the listed group
  • Member:  Real time list of online users are shown and user can contact other members through a private call
  • Friend:  Server and Local "Friends" can be selected to contact that are managed through the PTT Smart Dispatch software. 
  • Records:  Shows a listing of incoming and outgoing calls specific to the users radio.  Playback of missed calls is possible.
  • GPS:  Will show the location coordinates of the users radio based on GPS satellite reception.
  • Setup:  Provides control of PTT sound, back-light control, audio guide and a few other functions
A second option allows Retevis to sell a license to the Smart PTT Dispatch software for the user to install on a server they currently have.  This option lets the user manage all radios, group settings and view real time maps for all radios.  Pricing is negotiated with Retevis on this option directly.


While this may sound complicated, this approach creates a lot of very interesting capability, including the ability to manage radios on a private LTE networks which are growing in popularity in fields such as mining, agriculture and others.

Feedback on the RT-51

This may sound sort of funny, but Retevis should have included Wi-Fi in this product or at-least offered another version that included it. 

Had Wi-Fi been included, it would have allowed users an option for limited range "radio to radio" communication or to use the radio without the Smart PTT Dispatch software.  It would have also offered an option for brand loyalty and later upgrade capability dependent on user requirements such as in places where there is not good mobile network coverage, but good in building Wi-Fi connection.
Other "Network Radios" offer Wi-Fi  or even low power UHF as standard, so why not Retevis? 
There are reasons that the battery is slightly different than those in use by its popular VHF/UHF radios both in physical dimension and voltage, but it may have created more brand loyalty and interoperability to have used the same battery.



From a hardware perspective, there is not much else that should have been changed to keep this product at a moderate price point. Headset accessories are plentiful and uses the common Kenwood 2-pin configuration.

Key Comments

  • Battery life is excellent and only has shorter use time based on the GPS being on all the time, but can be shut off.  5 days with the radio powered on in standby mode was great and about 2 days with moderate use was common even with GPS on.
  • Direct competition for Retevis will likely come from Inrico and Peak PTT, but Retevis comes out ahead on price point.
  • Both competitors seem to have a more mature approach towards the software and dispatch management that are required for all network radios to work.

While a negative comment against Retevis, they may be able to innovate by investing in the Smart PTT Management Platform software development. 

In comparison,  Inrico has done well by integrating with the Zello and IRN PTT applications that are well known for providing "walkie talkie" like functionality on smartphones.

Peak PTT may be lesser known and will likely be the closest competitor to Retevis. The United States based competitor seems to offer better radio management software and features, but are more expensive than the RT-51.

RT-51 Final Verdict - Wearing Different Hats


  • The "Pretend Local Small Business Owner Hat" - The RT-51 is interesting for a business looking for reliable communication and not interested in maintaining any equipment aside from paying a monthly bill.  
  • The "Pretend Larger Business User Hat" - The RT-51 with its location tracking capability and ability to host the Smart PTT Platform locally will give control to the business owner with minimal infrastructure to maintain, especially if they already operate a computer server for other business functions.
  • The "Amateur Radio" Hat - The RT-51 will not be of interest to the amateur radio community without taking the radio apart to make it do something it is not intended for.
  • The "Communication Hacker" Hat - The RT-51 may be very interesting since this radio is nothing more than a cellular modem with various I/O capability. 
  • The "Concerned Family/Church Leader" Hat - The RT-51 monthly fee may be hard to handle, but a prepay data plan could be great peace of mind for for this solution over other unlicensed services when it is needed.  Group trips, community support and other non-commercial activity are great application examples for the RT-51.
  • The "Business Strategist Perspective Provider" Hat - The RT-51 is a great piece of hardware but will likely not do well from a sales perspective unless distributors and integration specialists are made aware of it.  The lack of polished software management and lack of known APIs will also prevent serious interest in this product since many will want full control of the hosted Smart PTT Platform rather than having it run somewhere unknown "in the cloud" since it can impact user privacy due to the embedded GPS capability. 
In Closing....

As an unlicensed communication tool, the RT-51 is a great idea, however paying a monthly fee to a mobile operator along with a very low annual server host or dedicated software license purchase outright that is hard to get clear pricing from the vendor, may create more business for the competition. 

Friendly Suggestion

Retevis has a great opportunity but really needs to look at where the real revenue and value is to its users as part of its sales and marketing strategy.

Biography on the author

Steve Bossert currently works for a Hong Kong based research & technology advisory firm. His role is to manage and grow the business visibility in North America for the unique capabilities of his company. Prior to this opportunity, he has worked for other well known strategic consultant firms over the past 15 years.  His expertise includes strategy for multinational semiconductor, mobile wireless, infrastructure and diverse emerging technology companies. 

Before graduating university and while in high school, Steve became a licensed amateur radio operator. Steve has the ability to blend his natural technology curiosity and business acumen to provide unique perspectives for both his professional and hobby interests.  Steve currently resides in New York with his wife Jennifer.






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