Iris+ and Fs TH9x range

I am only getting around 80 meters of range between the iris+ and the FS TH9x. This is quite a bit less than the expected range of 300m or so.

I am flying in a clear flat field in the middle of nowhere. GPS lock is easy to acquire and maintain.

When I hold the transmitter right next to the iris+ - it reads 99% rx. However if I walk 25 meters away the rx percentage drops down to Even at 20m - the rx percentage drops down to 55% or so.

I am making sure the battery in the IRIS+ and FS-TH9x are fully charged.

Where should I start to trouble shoot why I’m only getting 1/3 or so of the expected range.



That sounds like an antenna problem to me. If your IRIS is new, please contact If not, we can try finding out if the RX antenna(s) are broken or the TX antenna. RX is fairly cheap and easy to replace. TX not so much.

The radio that comes with the Iris+, leaves a little bit to be desired, in my opinion. I played around measuring the output, with an Immersion power meter, and the Iris+ radio was quite a bit lower on power, that either of my Spektrum radios. Here’s some tips from 3DR, scroll down, and there’s the thing about moving the antenna wires, but that has to do with GPS interference. Might help to open her up, and have a look see.

I opened up the iris+ shell and didn’t notice a problem. The GPS antennas seem in the correct placement.

Is there a relatively simple way to determine if I need to replace the antennas on the FS-TH9x or on the iris+?

The GPS thing is a different topic! If the RX antennas are too cloose to the GPS, it can negatively impact the GPS performance, because the FrSKY telemetry interferes with the GPS reception. But that has nothing to do with bad range of the remote control.

Please inspect the two antenna wires carefully if there’s any shard bend or nick. Especially, the top 2 or so cm which are without the outer hull. Those are the actual antennas. Also CAREFULLY wiggle the wires close to the RX a little bit. If they appear loose, that’s bad. They should move a little bit but not “rattle” inside of the RX.

Next step is to make sure, the antenna on the TX module is screwed down all the way and not loose. If that’s the case, unscrew it and check the connectors. One should have a pin in the middle, the other a hole. 2 Pins or 2 holes on either side would be bad. If you know anybody else with a FrSKY system, try swapping TX antennas. You can also use any WiFi antenna (watch the connector! There’s 2 versions! One with pin and one without pin on the antenna side!) E.g. I got myself a +9.5dB WiFi antenna with a magnetic mount and 2m cable which I put on a small 2m mast when I’m flying over forest. Works a treat and helps the range quite a bit :slight_smile:.

Actually, it’s the other way round, unless that part of the antenna is broken, it will be fine. It’s the receiving element. if you have a nick in the braided outer leading what is the antenna ‘element’ it can reduce the ability of the antenna to pick up signals.

The main problem with the Iris is the antenna are ‘jammed’ inside the hull. I improved reception in the Iris by running the antenna along the front legs of vehicle. You need to make a small recess in the cover where the cable exits the case, so as to not to pinch cable.

For the TX, as Stefan says it uses a RPSMA connector (not an SMA), which is compatible with WiFi antennas. You can experiment with higher gain antennas, but you can have other issues (Higher gain antennas have ‘blind’ spots closer in and above) 3.5dBi antenna is essentially the standard ‘no gain’ over the rubber duck type you have the radio.

You will also find that distance improves when you get off the ground, as being close to the ground effects the reception and transmission. (Hence Stefan’s suggestion of connection the antenna to a mast away from the ground, transmitter)