With regards to the MJX X-101 Quad and it's Transmitter:
I bought the X101 and also had a problem with the limited range which, for me, actually topped out at about 85 meters (depending on height, which I attributed to the Fresnel zone). After exceeding about 100 meters one day I wound up parked in a tall pine tree for a few days. After finally retrieving my quad, checking it out, and flying it again for a while the front left motor on mine also quit. After opening it up I found a trace on the PCB had fried completely in two! I repaired that with some wire but the motor still wouldn't run. Swapping the motor's wires on the board indicated it was the board and not the motor, so I ordered another controller board (receiver and four ESC all in one).
After installing the new PCB it paired up just fine so I can assure you you'll have no problem there.
Delighted by finally having my quad back (after waiting for the slow boat from China) I determined to do an antenna mod to boost it's range. I salvaged the antenna and cable from an old broken 2.4 GHz router I had laying around, but you can find the parts just about anywhere for dirt cheap. The "antenna looking piece" on the transmitter is actually nothing at all (it's empty) and the ACTUAL antenna is just hot glued to the inside bottom of the case. Split the case, remove the fake piece (some more hot glue found there) and original antenna, then solder the cable to the PCB and run it to the spot where the fake piece was. THIS is the hardest part of the whole mod: If you don't care, you can just epoxy or hot glue the helloutta the connector into the case and be done. Personally, I think that's kinda cheesy so I took the time to file on a washer and made a mounting adapter. Find a washer the same size (or close) as the bottom of the fake piece. You'll have to drill or file the hole to the right size for the SMA connector's threads to fit through and also file two small notches, exactly opposite each other, so the case will close completely. There are two protrusions in the case that make the rim the pieces fit into (the fake piece and the new mounting plate) which keeps everything from spinning. All this will become much more clear once you're actually looking at it all. With a standard 2 dB antenna I now get about 220 meters. If you are buying parts to do this then get a 5 dB antenna and you should hit the 300 meter mark easily.
That is well beyond line of sight !
DO WATCH the YouTube videos about antenna mods before trying this, even though they're not directly addressing this particular radio.
Finally, I have a question myself: My X-101 having decided to fly away to parts unknown (as they are want to do after going out of range) leaves me with this nicely modded transmitter but no bird to fly it by. I've decided to upgrade to 250 FPV quads and, not having the money for both a new Taranis X9D Plus (non-negotiable) AND a new quad too, can I use this MJX GR245 with either a Naze 32 or even better the Pro F3 through the X8R receiver ?