Improving cheap radio range

Radio range of my first drone, UDI 829A was pretty pathetic. OK, it was (still is, I only have to finally replace motors) pretty indestructible, quite stable and reasonably priced. But effective radio range as quite short. More less 50 meters. Above that limit strange things started to happen. The reason was pretty simple. Just take a look at this picture.

Can you see the transmitter antenna? Yeap, that it this short cable. Not only it does not go into "antenna cover" of the receiver, it is also horizontally polarized and when receiver is held in a normal way, pointing into a drone, it emits almost no signal in this direction. This and an additional single whip antenna on the receiver makes it virtually impossible to have a good radio range.

So, I've decided to fix that and install external antenna that would work with vertical linear polarization and actually emits some power in drone's direction.
This tutorial shows how to do it for UDI 829A, but will work almost all cheap drones. Their transmitters are very similar inside and as long as there is antenna pad or connector, it can be done.

1. We will need a transmitter, right?
2. This radio works at 2.4GHz so it is reasonable to install generic 2.4GHz WiFi antenna. They are cheap and easily available
3. Since WiFi antennas uses RP-SMA connectors, I've bought RP-SMA pigtail
4. Locate radio module. This will the one where original antenna is connected. Get rid of original antenna. Just unsolder it.
5. Also remove small connector from pigtail
6. Solder pigtail to radio module
7. Find a way to mount RP-SMA connector. I've chosen fake antenna and cut a hole in top of it
8. And then I filled everything with epoxy resin

This is how it looked at the end. Slightly absurd with such a big 5dBi antenna.

Later I replaced it with smaller 3dBi version taken from USB WiFi card.

Did it helped? I had no time to run some serious tests, but from one flight I would have to say that range improved more less twice. It was still working fine at more less 100m. When time allows I will do more tests. Vacation, where are you?