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Wednesday, April 25, 2018

Review: Xiaomi Mijia Dual Band Location Enabled HT

At the low end price tier of amateur radio hand held units we call "HT's", most hobbyists often consider the analog Baofeng and digital Radioddity or TYT models as entry level for under $60-70 USD each.

Xiaomi, which is a well known Chinese smart phone vendor unable to enter the United States market due to "intellectual property" issues with Apple and others. However, they also have a wide range of very high quality products ranging from mobile accessories and other electronics that do not suffer the same issue.

If you like the latest and greatest gadgets, this might be a good article to read.

In early 2017, Xiaomi launched a dual band hand held radio as a mobile accessory to allow for communication not reliant on a mobile cellular network.  The Xiaomi Mijia radio functions as a walkie-talkie and a blue-tooth to radio gateway for longer range communications not possible via short range communications like the Wi-Fi enabled FireChat and Serval applications.




Interesting features offered by the Xiaomi Mijia Two Way Radio

This product is unique for the following reasons:
  • Very easy to navigate and understand menu system 
  • Bluetooth pairing to smartphone for advanced location sharing and messaging
  • Unique memory management for licensed and unlicensed frequencies
  • Up to 2W RF output on 144-148 and 400-470 MHz
  • Share text messages, location and frequency with other users via APRS like functionality
  • High quality FM broadcast radio reception compared to other HT units.
  • Recharge by standard USB power cord
  • Under $50 USD per unit
Highlights of Xiaomi Mijia

When the product launched in 2017, the radio and Android mobile application only had Chinese language menus. Aside from my own translation with help by a friend of a friend, a community of users has since influenced Xiaomi to release an English update which makes this a better product for those unable to read Chinese. This review as a result has been a long time coming needless to say.

The English User Interface Experience

The radio itself only has a few buttons. On the front there are three that match soft menus at the bottom of the radio display, a two way up/down button for additional navigation, a side mounted PTT and top on/off/volume control.



The display is a high resolution LCD display with white back lighting that may remind some people of basic mobile phones before the smart phone age. Way back when, Nokia seemed to have had the most intuitive mobile devices of the day. Xiaomi seems to have looked back in history to influence the user experience of the Mijia. 

Navigation is easy to understand with no cryptic explanations of certain features, especially some of the more advanced functions like location sharing.

One of many classic Nokia phones
with a similar display as the Xiaomi Mijia
 
The Mijia easily pairs to a modern smartphone over blue-tooth. Compared to the Kenwood TH-D74 Tri-Band D-Star and APRS HT which retails for $600 USD and reviewed here a few months ago, blue-tooth functionality is much easier with the Xiaomi to use for things like firmware updating, messaging and memory management via the Android application called Mi PTT.

The Xiaomi Mijia interestingly enough is not really marketed to the ham radio community. 

Upon first use, you can only access low power 433 MHz frequencies that are also used by home weather stations and simple remote controls.

After you set up the Mijia with your smartphone however, it allows the user to unlock higher power transmit as well as expanded frequencies in the amateur radio spectrum.

This is a really smart way to get people interested in amateur radio in my opinion and keeps people who purchase a radio like this from accidentally transmitting where they should not, such as many documented cases with Baofeng type of radios that offer 136-174 MHz and 400-470 MHz coverage which create situations with users accidentally using first responder frequencies such as 462.975 MHz which is a common ambulance to hospital frequency across the United States.

The Xiaomi Mijia only allows 144-148 MHz coverage, but does permit expanded access to 400-470 MHz from the initial 430-440 MHz capability before expansion. In the United States, the UHF Amateur Radio band is 420-450 MHz in most parts of the country.  Elsewhere in the world, it is usually 430-440 MHz.  On VHF, outside the US and Canada, the VHF 2m band is only 144-146 MHz as a reminder.   This set up is smart by Xiaomi to show they care about compliance where other vendors do not.

While Xiaomi limited out of band transmit as best they can, it is still possible to transmit outside of the amateur radio spectrum on UHF band, so please be careful.

Memory storage is sorted into a few categories.  Preset frequencies for "Amateur Channel" and "Public Channel" offer low power options for local communications. The "Repeater List" group lets the user save different transmit and receive frequencies along with access tones call CTCSS or DPL. These are common terms in the amateur radio community.  Users of FRS type radios may know them as "quiet codes"
Easy memory management of the Xiaomi Mijia

It is even possible to save different VHF of UHF frequencies together in "Repeater List" mode which is not always easily done in many amateur radios unless using a computer to store them correctly, known as "split mode".

There is also a "Custom Channel" setting that permits any frequency to be entered, but not allow for repeater operation.  All frequency banks only store 20 channels each.

Beyond the use of simplex or "point to point" local communications or repeater operations for licensed amateur radio, another use case is the ability to use this radio for satellite operation in semi-duplex mode if you store the appropriate frequencies in the "Repeater List" storage bank. A basic article about this was released earlier this year on HVDN

An example would be to store the up-link frequency of 435.350 MHz with a transmit tone of 67.0 Hz in the "transmit" section and the down-link frequency of 145.880 MHz in the "receive" section in one of the 20 "Repeater List" slots.  Another example would be 145.8 MHz as the down-link and 144.49 MHz up-link which is in use on the International Space Station when over North America.  A special directive antenna would be needed to be heard by the satellite or space station, but you should be able to listen with even the included antenna.  Not bad for an inexpensive radio I would say.

Power In and Power Out

The internal battery which is not user accessible/replaceable is based on the common Panasonic 18650 lithium battery, so the radio can only output 2 watts compared to 5 watts or more with many comparable amateur handheld radios.

2 watts is often more than enough power for local and repeater based communications though, so is not that big of an issue for many users.

This 2 watt power level also encourages the user to experiment with different antennas to increase range without affecting battery life which is one of the fun aspects amateur radio enthusiasts enjoy.  Many of the unlicensed services such as FRS and MURS in the United States are not designed for this experimentation.

The antenna connector on the Xiaomi Mijia is known as a RP-SMA which is also the same as many of the Baofeng style radios. This is not as standard of a connector compared to the normal SMA connector found on a TYT, Yaesu, Alinco or Icom radios. A simple adapter can be purchased to convert the radio to use with other non RP-SMA antenna should you require it.

Xiaomi Mijia with supplied antenna connected


The antenna that comes with the radio is very short at less than 3 inches, but is optimized for the frequencies the radio is designed for. This can often not be said about the antenna that comes with a Baofeng type of radio though. Compared to a Baofeng UV-5R set to low power transmit, the Xiaomi outperformed it easily on both transmit and receive.

The Really Nice Features of the Xiaomi Mijia

The major function this radio offers its users is the ability to send location data and text messages plus create dynamic frequency destinations to allow many people to find each other and go to a different channel to avoid interference from each other.

Xiaomi Mijia showing the RP-SMA
antenna connector
Basic Location Functions

The Xiaomi provides a somewhat basic radar style location screen with the user location in the center of the screen and others in different radius shown at an approximate location and direction. For this to work, the radio needs to be paired to a smartphone with GPS enabled. You can view your own GPS coordinates on the radio which s not all too helpful, but you can also see the visualized basic location of other users relative to your position.

For those familiar with the TYT, Retevis and a few other DMR radios that include GPS, that feature is not very useful since radios like the popular MD-380 do not have this "radar" type of view.

The Xiaomi attempts a better approach to location sharing. The only better options are more expensive APRS enabled radios such as the Yaesu FT-2D, Icom ID-51 and Kenwood TH-D72 and D74 with none costing less than $300 and you need an amateur radio license.  The Xiaomi Mijia does this all for under $60 USD and offers license and unlicensed operation.

Xiaomi Mijia Basic Location "Radar Screen Mode" that shows other
users approximate location, distance and direction

Showing Latitude and Longitude after pressing the "Details" soft
button at bottom of display in "Radar Display Mode"

The bad news for amateur radio operators is the GPS data is not sent in standard 1200 baud AX.25 format that APRS uses. It seems the data speed is likely 4800 baud but is unconfirmed for now. This may be intentional by Xiaomi as to avoid competition with amateur radio vendors and potential interference.

Advanced Location Sharing and Text Messaging


When using the Mi PTT application on an Android smartphone is where things get interesting.

You can download free hyper detailed maps from Google for offline use where you may not have cellular network access or just use the maps in online mode where you have cellular network coverage.

Meet me at the white car in the second parking row? 
Yes, that level of detail is possible. 
This allows you to see specifically where your friends are each time they broadcast GPS location.

The Mijia lets you configure the radio to transmit automatically at a preset interval how frequently to share the location in order to conserve radio battery.

When the radio is paired with your smartphone over blue-tooth, the Mijia is used like a gateway to permit longer range communication when a mobile cellular network may not be available.

For those familiar with the GoTenna product, this is somewhat similar in function. The difference with the GoTenna is that it always needs a smartphone to perform any sort of communication since it has no built in two way voice function.

The original GoTenna as released after Hurricane Sandy to solve a problem. Cellular networks were not operable in the New York area and users could not communicate to each other. GoTenna used VHF MURS channels that are license free to send GPS location and text messages by acting as a gateway for your smartphone. The Xiaomi Mijia does the same function but is also a two way voice radio too. 
The Mijia is a walkie-talkie first compared to GoTenna so can be used without a smartphone, but gains much more functionality when used with a smartphone, just like a GoTenna.  Even if you do not have your smartphone, the Mijia still works like a walkie talkie to tell your friends verbally "Hey, where are you?  Not that parking lot, the other one. I am near the trail entrance."  Having a smartphone allows much more efficient communication though to just send the location so there is no confusion.

If you want to text message a friend, you just find them on the map on your smartphone and you can open up a messaging tool. Your radio then sends your text message typed on your smartphone over blue-tooth to your Mijia where it actually transmits over the chosen frequency from the Mijia.  Right now there is no function to share pictures over the Mijia, but that may be possible in the future if the files are compressed enough to be sent to other users.

The Xiaomi Mijia does not provide mesh networking like the latest GoTenna (Earlier version did not have that function), but comes close in that the user can let others know what frequency they are on by sharing that information on a common channel to ensure all users can eventually text and voice communicate together. This common frequency for what Xiaomi calls "Fast Teaming" was not initially changeable in earlier releases, but it seems that has changed with the latest firmware as of the time of this article.
Fast Teaming lets you find your friends
when on different channel

Think of this feature as if you had a 40 channel CB walkie talkie back in the 1980's.  If 2 of your friends were on channel 14  (27.125 MHz) and 4 others were on channel 38 (27.385 MHz), what would happen when when you missed hearing when people were moving frequencies.  This "Fast Teaming" function tries to solve that problem. You can send over a common channel that is secretly listening in the background at all times on the Mijia what frequency everyone is headed to and you can easily meet them there.   Those familiar with a Baofeng radio will know this function as "Dual Watch", but the Mijia does this much better by providing a useful application of it.

Other Features That Enhance Enjoyment Outdoors

The "Dual Watch" function already mentioned allows you to have two channels monitored at the same time of your choosing.  The Xiaomi also inputs a third frequency that is used for "Fast Teaming" also, so technically the radio will look at three channels rapidly for incoming signals.

On a more technical side, the Xiaomi Mijia internal design is based on the AT1846S and RDA 5802N chips found in many other modern radios but has always suffered a bad reputation as being fairly broad banded "software defined radio" that are easily overloaded by strong signals.

To solve this, better filtering for receive and transmit are needed and are commonly called the "RF Front End" in engineer language.

The Xiaomi Mijia seems to have incorporated better design principles compared to Baofeng and TYT radios and this also extends to the audio quality found in the built in FM broadcast capability.  If plugging in a pair of headphones to the bottom of the radio, stereo sound is output compared to the mono audio that other "ham radios with FM broadcast reception" provide. Transmit and receive audio when communicating are also very good and not what one would expect from a low price radio like the Mijia.


Another nice feature with the Xiaomi Mijia is the standard USB mini port found on all but the absolute latest Android smartphones using USB 3.0.  You do not need a special charger or cable for the Xiaomi whereas most all traditional "ham radios" do. Moreover,  ff you are a hiker, biker, camper, runner, etc and have a USB power bank, you could charge the Mijia from that same power bank, much like you would charge your smartphone from. 


What is not to like about Xiaomi Mijia?

Even though this may sound like a very positive review of this product, there are a few things not to like.

  • Depending on where you purchase the radio from, you may need to figure out how to upgrade from earlier firmware to the latest English version. 
  • Another issue will be finding the Xiaomi Android application since it is not currently available on the Google Play store in the United States.  
  • You will need to likely enable "Developer Mode" on your Android phone and allow 3rd party unsigned applications to be installed if you find the application elsewhere on the internet such as here
Beyond the language and localization issues, the Xiaomi Mijia feels in the hand like a quality product costing much more.  It also does not seem like a "scary gadget" to those opposed to many confusing buttons or features.

The only major thing I would have liked was for inter-operable features with standard amateur APRS equipment, but that may leave some room for those that like to tinker with firmware.

Lastly, the USB connector seems to only allow for charging, not access to the radio itself. Firmware updates are done over blue-tooth, so that has to be where a "backdoor" into the Mijia exists and worth exploring.

Where to purchase?

Amazon offers many stores that stock the Xiaomi Mijia.  I had originally purchased from Alibaba as well as another Chinese wholesaler last year. The pricing in the last year has fluctuated a little, but not much.  The white models shown here were the only ones available at the time. The dark gray version seems to sometimes become available.




Translation:  China promotes ham radio to non ham radio people who see value radio. Why cant Amateur radio vendors offer a "stepping stone" type of product too?  

One thing that does excite me is that the Mi PTT app does promote that and offers basic licensing guidance for those interested in amateur radio.  Perhaps China is more forward thinking in promoting amateur radio than in the US through products like this.  Only time will tell if the US will try to bring a convergence lifestyle product like this to market....














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