For long range flying, RC links is just as important as your FPV video link. In this review we will have a look at some long range RC options: the Frsky R9M and TBS Crossfire. These are the two most popular TX modules compatible with the Taranis X9D and QX7 transmitters.
Check out this article to learn about the basics of a radio transmitters and receivers.
You can get FrSky R9M bundle with R9 Receiver
You can get TBS Crossfire modules from:
TL;DR – R9M or Crossfire?
Frsky’s R9M system is much cheaper than the Crossfire, but the Crossfire has better features. In the end of the day, it comes down to which company you want to support and what you can afford.
|R9M||R9M Lite||Crossfire TX||Crossfire Micro TX|
|915MHz (US, Asia, AU)
|Smallest RX||R9 Mini RX ($13)||Crossfire Nano RX ($40)|
If you plan to fly long range, it doesn’t matter which system you choose, the limiting factor is still the video link. In theory it will even out-perform 1.2GHz video link.
Yes, Crossfire is slightly faster than SBUS, but not everyone can notice the milli-second level difference, especially when you are flying long range.
Why 900MHz for Long Range?
2.4GHz is the most common frequency used by radio transmitters, by using the built-in TX module, you can probably get a few hundreds meters of range from a Flysky TX, 1 miles from a Frsky Taranis at best.
The reason that the Frsky R9M and TBS Crossfire can do multiple miles is because they are broadcasting at much lower frequency, i.e. around 900MHz.
As explained in our TX buyer’s guide, lower frequency is better at penetrating obstacles, however the downside is the relatively large antennas.
Luckily the antennas in these two modules we are reviewing are compact enough for easy transportation and installation in mini quads or wings.
Be aware that 900MHz is not legal for hobbyists to use in every country, because that’s the frequency our mobile phones operate at as well. For that reason we can only use 868Mhz in Europe, and 915Mhz anywhere else. Make sure you check your local regulation before broadcasting.
I have some tips about long range flying you might find interesting.
FrSky R9M module and R9 receiver
FrSky’s previously released a long range receiver L9R for the Taranis’s 2.4GHz system. The new R9M TX module and R9 receiver is for the 868/915Mhz frequency.
R9M has the same size and look of the 2.4Ghz XJT module.
What’s in the box?:
- R9M Module
- RP-SMA Dipole Antenna
- Instruction Manual
- R9 Receiver with “T” Antennas
R9M TX Module
R9M Module has switches for choosing the transmitting power, Smart Port, RS232 Serial Port Function Button and LED light indicator.
Operating frequency (868Mhz vs. 915Mhz) can be selected by flashing the module with dedicated firmware.
NOTE: We have been supplied with an earlier version of the R9M without the XT30 socket.
- 2 power settings in EU Version Telemetry: 25mW (with telemetry) and 500mW (without telemetry)
- 4 power settings in Non-EU Version: 10mW, 100mW, 500mW, 1000mW (all with telemetry)
- Micro USB port for firmware updates
R9 RX Spec:
- Dimension: 43mm x 27mm x 14mm
- Weight: 16g
- Power Input: 3.5V-10V
- Range: 10km+
- EU Version: 8 Channels with telemetry and 16 Channels without telemetry
- Non-EU Version: 16 Channels with telemetry
- Supports redundancy function
- MMCX antenna connector
The R9 receiver has similar size to the X8R, and it’s enclosed in a plastic case. Taking apart the RX, we can see there are two PCB’s stacked together.
Dedicated RSSI pad is highlighted below.
R9 comes with “T” style antennas. Instead of tube or wires it has plates with the antenna active elements imprinted on them. It was quad and to capture those tiny tracks on the plates though. Plates itself are very thin and flexible.
Correct antenna placement for the R9 is on the photo below. Both plates need to be 90 degrees to each other.
The R9 is currently the only receiver that works with the R9M module, but we have heard news about the “R9 Slim” to be released soon, which is basically a smaller and lighter version of the R9 for smaller copters.
Update (Apr 2018): Frsky released a smaller receiver – The R9 Slim RX.
Crossfire TX, Micro TX and Micro V2 Receiver
Crossfire is developed by TeamBlackSheep (TBS) and has been on the market for years now. They offer two TX modules:
- Crossfire (often called “Crossfire Full”)
- Crossfire Micro
Incompatibility With Frsky Taranis Q X7 & Q X7S
There is a bug when using the Crossfire with Taranis Q X7 or Q X7S, where the Taranis would constantly shout out warnings “Telemetry Lost”.
This is caused by changes FrSky made to the hardware in the latest QX7 and QX7S, which results in Crossfire modules can’t operate at full baud rate in these radios.
There is a DIY hardware mod required to fix this issue if you plan to use the Crossfire with the Taranis QX7, which involves installing a small chip inside of your radio (the chip comes with your Crossfire).
However this issue does not affect the Taranis X9D-Plus and some very early batches of QX7, and they are fully compatible with the Crossfire out of the box.
Crossfire “Full” Transmitter Module
- 5 power settings – 10mw, 25mW, 100mw, 500mw, 1000mw, 2000mw
- CRSF protocol, lower latency than Frsky’s protocol (more info)
- 8 / 12 channel output via PPM/SBUS/CRSF
- Transmitter LED shows link health
- Built in OLED display for easy configuration
- You can update receivers wirelessly
- Micro USB port for firmware updates
- Comes with SMA dipole antenna
- Bluetooth module
- Spectrum analyzer
- Operating frequency (868Mhz & 915Mhz) can be selected from the OLED screen menu
The Crossfire “Full” module requires some assembling before you can attach it to the radio.
It comes with a JR bay adapter that has sticky foam on the back. There are 4 pins in the adapter that have to be aligned with the holes in the module itself. Two wires coming from the adapter are going to RC Input and Exp.Port. They are of a different sizes so it’s easy to figure out what plug goes where. Once connected the Crossfire is ready to use.
The Crossfire module requires external power source when using 1W and 2W mode via the XT30 connector.
OLED display can be use for configuration of the module and receivers but also it has a few useful functions like spectrum analyser and find mode which helps to located lost aircraft. If the quad has a TBS GPS attached (via FPV vision or TBS Powercube) it can even show the GPS coordinates. This module is just packed with useful features!
The GPS coordinates are useful for finding lost models, and I tested it and the accuracy was within 5-10 meters.
Crossfire Micro Transmitter Module
The Crossfire Micro TX module is a smaller / lower power version of the Crossfire “Full” module. It can fit inside the Taranis external module bay without any adapter.
- 868Mhz (EU/Russia), 915Mhz International frequency
- Dimensions 66 x 48 x 21 mm. 47g of weight
- Built in Telemetry
- 2 power settings – 25mW
- and 100mw
- CRSF protocol
- Low latency, 150Hz update rate
- 8 / 12 channel output via PPM/SBUS/CRSF
- Transmitter LED shows link health
- Receiver “over the air” update
- Micro USB for firmware updates
- SMA dipole antenna
- Configuration of the module and RX can be set using Taranis LUA script, including changing operating frequency of 868MHz and 915MHz
The Crossfire Micro has no OLED display and all the configuration can only be done via LUA script.
Before binding a receiver, you can put the TX module in bind mode by pressing the button in the middle of the module.
There are only two power settings available: 25mW and 100mw, there is no external power source needed for such low output power.
Crossfire Micro V2 Receiver
- Dimensions: 40mm x 15mm x 10mm.
- Weight: 3g
- BST port expandability
- Receiver firmware can be updated wirelessly from the TX module
- Comes with two U.FL antennas (one spare)
- Comes with BST wires, standard connector wire and servo adapter
The white wire is the Active part of the antenna while the black wire is the ground plane.
The best way to install the antenna is to keep both wires opposite to each other (180 degrees) and perpendicular to the shielded antenna wire (90 degree), like a “T” shape.
Best to keep the antenna vertically but horizontal placement (makes more sense on a mini quad) is also fine but not for crazy long distances.
TBS also offer a ready made antenna called the “Immortal”. It has better protection against crashes and it’s easier to mount in a mini quad.
Crossfire Full vs Micro – Which version to choose?
The Crossfire Full version is over twice as expensive as the Micro ($209 vs $99), is it twice as better? Let’s take a closer look at the differences between the two TX modules.
The Crossfire Full has the following features that the Micro doesn’t:
- OLED Screen for configuration
- Bluetooth module (for telemetry distribution to tablet or a laptop)
- Output Power up to 2000mW (2W) vs the 100mW of the Micro
Both modules supports LUA script so changing configurations are equally easily.
For FPV mini quad racers, the Micro TX should fulfill most of the requirements. It’s been reported that the Crossfire Micro RC link has 10Km range or even further depends on the condition. Can your mini quad travel 20Km with a 1300mAh battery pack? Probably not :) So that range is more than enough.
If I was getting the Crossfire Full version, it would because of the OLED screen and the features that come with it. The extra range that it offers would probably be a bonus too.
The built-in Bluetooth module is the least important consideration in my opinion.
The Pro’s and Con’s of Frsky R9M and TBS Crossfire
What I liked about the FrSky R9M and R9 combo?
- Compact TX module
- It’s a FrSky product, so it’s fully compatible with the Taranis radios
- Removable antennas with MMCX connectors on the R9 receiver. Making it easy to replace without worrying of damaging the socket
- Very good price at $99 for both TX module and RX
What I don’t like about the FrSky R9M and R9 combo?
- Switching power settings can only be changed using dip switches, you cannot change settings using Taranis LUA script
- Only one compatible receiver available (at the time of writing this article)
- R9 receiver is a bit large for mini quads (but it’s fine for wings and airplanes)
- R9 receiver antennas have an unique shape that is tricky to mount on a small aircraft
- Fewer power options than on Crossfire
- The R9M unit we received was sitting a bit loose in the JR module bay
- Instruction manuals could be better
What I liked about the TBS Crossfire system?
- Flexible options, users can choose between Full & Micro version depending on budget, range requirement and features
- Good selection of transmitting powers (makes it flexible since the regulations are different in every country)
- Lost-Model-Search mode and last GPS coordinates can be shown on the Crossfire “full” module OLED display
- Configuration can be changed via OLED display (on the “Full” version) and LUA script (on the Micro version)
- Compact and light weight receiver
- Informative & well written instruction manuals
What I don’t like about the TBS Crossfire system?
- The Crossfire “Full” module is more expensive ($209), Micro is the same price
- DIY Mod is needed to use with Taranis Q7X, good soldering skills are essential
- The LUA script feature is still buggy, it does not always work with the Micro module, sometimes it doesn’t even connect at all
- The U.FL connector on Micro V2 RX is fragile and prone to damage
- The Crossfire “full” version is a bit bulky and sticks out a bit from the back of the radio. It’s more likely to get damaged if not protected properly
Happy flying !
Picture Credit: Artur Banach