Just want to share with you how I did the Taranis X9D antenna mod – replacing the original 2dB antenna with a RP-SMA pigtail, making the antenna removable so I can use a 5dB dipole antenna, or 2dB whenever I want.
See other mods I have done to the Taranis X9D.
Risk Warning
Beware that this is a risky mod, some have reported damages to their Taranis after doing the antenna mod.
I removed the antenna and soldered it back when I was swapping the housing 18 months ago, and it’s been working fine since. So that tells me that if you do it correctly, it’s fine. But still, try to avoid messing with delicate electronics.
The reason I am doing this is because the original 2dB antenna is broken. Rather than replacing it, I might as well go a step further and put an RP-SMA pigtail in there.
If your Taranis is working fine, maybe it’s not worth the risk :) Anyway if you are interested in doing so, follow along and I will show you how :)
If you purely want more range, consider the Frsky R9M, or Crossfire.
The Benefit of 5dB Antenna
This is what the radiation pattern of a 2dB antenna would look like. It’s almost omni-directional, covering the space relatively evenly around the antenna. That’s great if you fly mini quads and micro quads normally just around yourself.
The higher gain of a 5dB antenna changes the shape of radiation pattern to be more directional, giving you more range on the sides and less range on top and bottom. This allows you to fly longer range assuming you are placing the antenna in the upright position. But signal is going to be much worse than the 2dB if your antenna is pointing directly at the model.
Anyway with the RP-SMA connector, you can remove your antenna for easier transportation. And you can also use 2dB or 5dB antenna, whichever you prefer.
Shopping List
Here are the parts I bought, only $10 bucks.
- RP-SMA Pigtail with 5dB Antenna Kit: http://bit.ly/2Cacrnd
- 2dB Antenna: http://bit.ly/2QsWcKU
Some reported issue with the 5dB antenna, but works fine with 2dB. So maybe it’s best to grab both antennas when you are doing this mod just in case. Anyway my unit works fine on both antennas after the mod.
Anti-Static Wrist Strap: https://amzn.to/2Z5D1IC
Not necessary but recommended, it helps protect your Taranis during the mod. If you don’t use this, make sure to “ground yourself” to discharge static electricity by touching grounded conductive surface.
RP-SMA Male to Female Adapter: https://amzn.to/318tym7
Note that SMA connectors have a finite mating cycle of about 500 times. It won’t just suddenly stop working at the 500th time you plug it in, but the RF performance will decrease over time the more often you remove/install the antenna. Over-tighten the antenna can also reduce the lifespan.
Therefore some people get an RP-SMA adapter between the antenna and pigtail, so it will only wear out the $2 adapter and not the pigtail. However the adapter will result in a slight signal loss, so that’s your call.
Remove Hot Glue
Ground yourself before continuing.
Open the Taranis housing. Find where the original antenna is soldered to. Remove hot glue – isopropyl alcohol is great for removing hot glue.
Desolder Original Antenna
Now you can desolder the original coax cable. Take a picture of what the solder joint looks like for reference. Avoid overheating the pads.
Remove Original Antenna
Once the antenna is desoldered, you can pull it out of the top socket. There are two clips holding the antenna in place, you just need to squeeze them with a pair of pliers and push it out of the socket.
Install & Solder RP-SMA Pigtail
Install the RP-SMA pigtail in the socket like so before soldering it to the PCB.
Add Hot Glue
Finally add hot glue to these places.
Check SWR (RAS)
To find out whether you’ve done the antenna mod successfully, check SWR (standing wave ratio). It’s a measurement that indicates the amount of signal being transmitted versus reflected back from the antenna.
It’s a good way to determine if you have a problem with the antenna, or if the antenna mod was done incorrectly. A lot of energy will get bounced back and the SWR would be higher than usual.
The lower SWR the better, ideally it should be around 0 to 1. You can put your hand around the antenna and the reading may increase slightly, and if you put the antenna in something like a metal box or foil paper it may even go up to something like 16 or higher. That’s showing its normal operation.
Since OpenTX 2.2, SWR has been renamed to RAS (Relative Antenna Status) in the Taranis, and moved from Telemetry Page to the Analog Test Page in Radio Setup (hold down menu button, and go to page 7).
Note that sometimes crappy antenna can give you high SWR value. If this happens to you, don’t panic, try a different antenna first!
8 comments
I did this mod a few years ago to fit a high gain and so far it’s worked well. I’ve gone 4Km on a regular Rx, indeed you do have to point it right at that distance. I don’t take my antenna off, it stays on permanently. I was once regularly removing the antenna on a different radio and that lead to trouble, the connectors are not robust enough for that.
The mod worked really well for me.
I have been using a 2.4 moxon antenna but would prefer a more directional antenna.
Being a ham radio operator for decades and successfully building my own antennae let me throw in some info. When making this mod, one has to take into consideration the length of coax from the board solder point to the SMA connector (the SMA pigtail). If it is just cut to a random length more likely than not you will eventually fry the board. A good video for determining the length is youtube.com/watch?v=-8R1rPZulrY he goes into the formula for the coax length.
I refer to this length of coax as a balun or matching transformer. The balun acts as an impedance match between the antenna and the board. If cut to the wrong length it causes an impedance mismatch which can/will over time fry things, if cut to the correct length, the board doesn’t ‘see’ an impedance mismatch so it is happy. And i would NEVER trust the RAS readings in the Taranis after making an antenna mod unless i backed them up by using a calibrated SWR meter.
With the new mod you could/should purchase/build a good SWR meter to temporarily put in between the new SMA connector and the new antenna to get a true SWR reading as well as ‘tuning’ (adjusting the new antenna to correct length) any antenna you wish.
BTW, on github, there is a post concerning the RAS switch around that is very interesting. It causes me to believe the RAS is not what I would want to trust to tell me if my antenna is functioning properly This post is probably 1-2 years old.
Yes you are totally right.
That’s why I recommended these kits as they are pre-cut to the required length.
You mention the SMA pigtail’s length and about ensuring it is the correct length since it acts as a coax balun. I’ve never known a simple whip antenna (which is all the stock antenna is) to require a matching transformer but if you say it does, I’ll not argue that point. So….my question, how do you take into account the extra SWR meter’s RF path and the coax cable many people would use? Certainly, that must change the distance between the RF board and the antenna itself. Does not velocity factor also come into play when working with a coax balun? Is the replacement pigtail’s VF the same as the section of coax that is being replaced? These were some of the questions going through my head as I read your warning for this antenna replacement project.
I did the mod a year ago and immediately had reduced range with the Taranis. Later that year I bought the Taranis SE, which after about a month produced serious connection problems.
The V2 of the Taranis SE I got in exchange was a bit more stable, however, the day after I put the 5db antenna on I faced a loss of about 30% in range, even with the old antenna back on again.
I guess it is no wonder that aloft.com is no longer selling Taranis with removable antenna. The devil seem to be in the detail and FrSky is at least until now not exactly successful in mastering that.
Same happened to me, was fine about 5-6 months (range was excellent) and then I had to replace my rf board.
I strongly recommend against this mod. Me and another guy I know did it and at first, it was great. I flew a quad out to about 2 miles with this mod and a regular X4r! The quad actually crashed out there and that was an adventure to get it back, but it wasn’t the Taranis’s fault.
The reason I recommend against it is both our boards fried over time and we had to replace them.
Here’s the 2 mile run and crash:
youtu.be/nD8zwz0tJww