Phantom Transmitter/Receiver Upgrade Futaba T14SG/R7008SB

My DJI Phantom with Futaba R7008SB receiver and
T14SB transmitter. Telemetry now included!

The international version of my blog is still lagging behind, but I try to slowly catch up. So here we start with Pimp My Phantom...

The DJI Phantom comes ready to fly and so the box includes only a simple and inexpensive 2.4GHz transmitter to keep the box price low.
Update: Meanwhile, DJI has improved the Phantom's transmitter and receiver. While the company now markets this improvement as a frequency hopping system, measurements show that the new system only uses four discrete frequencies, so this is still a very simple system.
After having flown the Phantom with great pleasure for several ten of hours I wanted more comfort and more reliability than just what the beginner's level has to offer. I wanted more reliability of the radio link even in difficult locations with many reflections, automatic timers for monitoring the flight battery, and also a proper slide lever for controlling the camera for my future gimbal upgrade.

After touring the local electronics chain store I picked up a Futaba T14SG transmitter that also comes with a suitable R7008SB receiver. This combination features flight battery telemetry, that is, the receiver send back the battery voltage to the transmitter. Don't declare me nuts, read on for my story of upgrading my Phantom...

Which Transmitter to Choose From?

Me, being a complete beginner when it comes to radio-controlled models, faced the task of choosing a suitable 2.4GHz transmitter from the large and confusing market for RC transmitters. But fortunately, gone are the days of 35MHz technology with its expensive and delicate crystals. Back then, those transmitters seemingly were developped by sadists, judging from their user interfaces and manuals.

My wish list consisted of:
  • in any case, the transmitter had to support at least 7 channels, better 8 and more channels.
  • the radio link had to use a much better transmission method than the bare DJI transmitter; so this was surely an easy goal to achieve.
  • the transmitter must have at least two 3-position switches in order to support the Phantom's flight mode and IOC mode selection. Luckily, gone are the days where the transmitters barely came with any switch so you had to purchase and mount them separately. Judging from the available transmitters, most customers now want fully equipped transmitters.
  • a slide lever for future gimbal control. This will allow the camera to be tilted while in flight.
  • a decent user interface, and that does not include these old LCDs with just two lines of a few characters each. I'm still remembering the chaotic and structureless mc-20 user interface Graupner did many years ago. Word has it that Graupner may actually be able to improve.
  • optionally, if possible, S.BUS support. I don't want to deal with a bunch of servo patch cables between the radio receiver and the Naza-M flight controller.
Years ago I already had come across robbe/Futaba and JR/Graupner, so these were already kind of household names for me. But in the end I went for the Futaba T14SG transmitter.

Futaba T14SG radio transmitter with R7008SB receiver that comes with telemetry. Sweet!

An important reason for my decision for Futaba is that they use a real channel hopping mechanism all the time, hopping after a few milliseconds. If I have been informed correctly, then JR/Graupner instead uses only two channels for hopping, selecting them through measurement when the transmitter is switched on. To me, this isn't going to cut the mustard, as for some real reason the many IEEE 802.11 radios all work with true channel hopping.

I don't need 14 channels, but the T14SG has something else of real value to offer to us pilots flying battery-powered RC models: telemetry. This feature strongly influenced my decision to go for the Futaba T14SG and not for some less sophisticated Futaba or JR system. This way, I'm always informed about the true flight battery voltage and don't need timers to guess about the battery status of my Phantom! I purchased the T14SG as a set coming also with the R7008SB receiver. The R7008SB support S.BUS operation and additionally the newer S.BUS2 variant. S.BUS support was also of importance to me in order to have only a single cable connecting the receiver with the Naza-M flight controller of the Phantom.

Craz Telemetry: Receivers are Sending!

Phantom flight battery feedback. Great!
So what is telemetry? A simple, yet incredible useful feature: the receiver in your Phantom is now able to send back(!) information to your radio tranceiver. This way, I'm always informed about the current battery voltage of the flight batteries. In addition, I'm also getting feedback about the signal strength that the receiver acutally sees. This information is then displayed in the transmitter's LCD.

In order to make real use of this feature you'll need the separately sold Futaba external voltage cable (reference number FUTM5551 CA-RVIN-700 EX VLT CBL). The battery voltage used to power the receiver itself is of no real use, as the Phantom stablizes it so it is around 5.5V or 5.6V all the time. In case you are curious, the S.BUS cable or alternatively the servo patch cables not only carry the signals but also power for the receiver.

In my experience: I couldn't notice any reduction of flight time due to the telemetry function. With the tiny amount of telemetry data to send only once a second the receiver barely needs any really noticeable amount of sending energy, compared to what the motors are sucking.

The Upgrade Looks Simple Enough to Me... 

You need to remove these four screws on each arm.
Luckily, opening your Phantom is easy, thanks to DJI's video about upgrading your Phantom, where you see the necessary procedure in the first part of the upgrade video.

In case you sticked the red self-adhesive stickers to the forearms, you should first cut them using a really sharp knife along the edge between the top and bottom housing parts.

You will need these tools:
Important! Watch out so you really use a Philips screwdriver and not a Pozidriv. These two look very similar, however using a Pozidriv on a Philips screw can damage the screw head and you will have difficulties loosening such a damaged screw again. In such cases, a simple flat-head (slot) screwdriver with an 1,5mm head may come to your rescue.

You next need to unscrew the two screws that are holding the original DJI receiver in place. Then you can simply remove it. Again, use a really sharp knife to cut into the silica blob that fixes the connector cable between the receiver PCB and the Naza-M flight controller. You can later use this cable to connect the Naza-M to your new Futaba R7008SB receiver. Make sure to remove any silica left-overs from the connector to avoid any later problems with the connector.

Firmware Update Naza-M

There is an important thing to watch for in case you want to use any of the newer Futaba receivers with S.BUS2 functionality, otherwise your upgrade literally won't fly:
Attention! You'll need to upgrade the Naza-M flight controller to at least firmware release 3.16 or later. Older firmwares don't understand the S.BUS2 protocol and also don't understand the slightly modified S.BUS protocol as spoken by receivers such as the Futaba R7008SB or R7003SB.
For the details about the Naza-M firmware upgrade, please consult DJI's support web pages. They really do a decent job in explaining and illustrating what to do. Just make sure you have a working USB cable. Again, Arthur Kunze comes to rescue with a video on firmware upgrades. Please head over to his channel for details.

The Modification

Fixing the new R7008SB receiver.
Removing the old DJI receiver went almost smooth, except for one screw that tried to resist. In the end, it quickly caved in.

Putting in the new Futaba R7008SB was an easy and painless job.

And while you are at it, you should solder the adaptor cable for external voltage FUTM5551 CA-RVIN-700 EX VLT CBL to the Phantom's central board. I used the existing spare red/gray cables for this purpose. You don't need this cable for the future gimbal and this way I don't need to solder directly on the central board. At least I thought so ... but judging from the documentation for the new Phantom connection main board everything will be different then when I will be upgrading my Phantom with a Zenmuse H3-2D gimbal. Sigh.

3M Dual Lock
For fixing the receiver I'm using 3M Dual Lock that I rather got by accident while being on a weekend dive tour in the Lausitz, a beautiful region in the far east part of Germany. The till girl was carefully analysing this product she probably never had recognized before when I purchased four packs at once.

Of course, you can also use the usual self-adhesive velcro strips that many companies offer. However, the 3M Dual Lock strips seem to have better cohesion due to their different hooklet design (but forget about the marketing babbling that is printed on the package).

Simple and plain wiring thanks to S.BUS2.
Right placement of the R7008SB when using the
basic Phantom main board.
You then connect the new receiver to the Naza-M flight controller using the existing receiver module cable. It needs to link the S.BUS2 connector of the R7008SB with the X2 connector of the Naza-M. Please remember that for this to work, you need a Naza-M firmware release of 3.16 or later.

In principle, you might also be able to use the Ch7/S.BUS connector. But for this you need to reprogram the receiver, which is a real headache to carry out. And since the Naza-M supports S.BUS2 operation, there's no need for S.BUS anyway, so I didn't tried it.

Left placement of R7008SB with the integrated Phantom
connection kit main board.
The receiver placement shown above only works for the basic Phantom main board, that is, the one that comes built-in when you order a Phantom. If you happen to upgrade to the integrated GCU and PMUv2 Phantom connection kit main board, things are different. In this case, you need to place the R7008SB receiver on the left of the Naza-M chip.

The reason is that the Naza-M has been slightly moved to the right and this just leaves enough room for the original simple receiver module. Unfortunately, there isn't enough room now for the R7008SB on the right side, so you need to place it on the left side. Please make sure that you leave some room between the receiver and some circuit packages on the main board, so air can still flow across these circuits.

Placing the Antennae

First, you should ensure to properly place the two antennae cables of the Futaba R7008SB receiver. Futaba advises to place them in an angle of 90° to each other. However, note that you don't need to keep this rule over the full length of the antennae cables but only for the final few centimeters (or inches, you know). Only the non-shielded part counts as an antenna. You can easily identify this part as the cable only has a transparent isolation in this region, while the remaining part has an opaque gray shielding.

You should also make sure to keep the antennae away from the motor controllers and their power supply wiring. This is easier said than done, so the antennae placement you see in my pictures is only a suggestion. Your mileage may vary...

As can be seen from the image above I placed the antennae cables as follows
  • antenna 1 goes straight to the nearest  feed through and then down the landing structure. You may fix this antenna in a similar way as the original DJI antenna using some self-adhesive duct.
  • antenna 2 stays inside the Phantom's casing. Going along the receiver it then turns 90° to the left and then behind the Naza-M chip. This way, the real antenna end is kept away from the ESCs.

Pairing Ritual

Pairing the receiver to the T14SG transmitter worked perfectly ... but only after I managed to understand that one needs to first switch the transmitter into pairing mode and only then switch on the receiver. The manual says so, I just need to read it thoroughly...

From a safety point of view this absolutely makes sense. This way, you only can reprogram a receiver immediately at power on, but never while in flight. My fault was that I still had the DJI instructions in mind which are different, as their receiver has a small button to but it into pairing mode.

Wiring the R7008SB Up to the Naza-M V1

Naza-M V1 firmware 3.16: finally, S.BUS2 support.
In order to complete the receiver replacement, you need the Naza-M assistent software to tell the Naza-M flight controller that it is connected via S.BUS(2) to its receiver. Probably due to trademark/legal reasons, DJI calls the required operation mode D-BUS. So don't be confused, just switch to D-BUS operation as this covers S.BUS and S.BUS2 operation.

You'll find the required setting when you go to the Basic page of the Naza-M assistent software. There, select the RC tab. There, select D-BUS as the Receiver Type. Don't forget to recalibrate the command sticks. However, better first program the transmitter first before recalibrating.

I'm explaining the details of how to program the Futaba transmitter T14SG in a separate follow-up article. This article is already unwidely enough.

It Flies Again!

After reassembly, control that all screws are in their right places and are properly tightened. After I checked everything I then went to a suitable place nearby for my first flight with the new transmitter and receiver. My check flights immediately went smooth right from the start. So, for the moment, the upgrade is done, next comes fine-tuning the settings.