I will share to you the repair and enhacement procedure i did to my Turnigy 9X8Cv2 receiver.
The Rx comes with a minimal antenna, possibly 2dBi, monopole type.
It's made of a full wavelenght mini coax cable, a sleeve balun to avoid detune from coax, and a 1/4 wavelenght element (the same coax, but stripped).
The Coax is very weak, and tends to reak in the point it leaves the box. In my case, it was ripped off by one prop, in a flip-over small crash.
since the feed cable is exactly one wavelenght (12,5cm), we can remove it entirely, or rplace with same lenght. intermediate lenghts will detune the antenna.
I decided to remove the entire cable, and solder a board-mount rp-sma male connector. this way i can attach any antena i want.
here you can see the solder piont for antenna.
to desolder, i used adesoldering iron, along with the normal iron.
and the connector was donated by an old USB wifi adapter that no longer works:
the desoldering iron (stain sucking iron) was useful on removing the connector from the donator.
here you can see the back of the Rx board. there is another feed point, exactly like the one on the other side. this one is preferable to fit the connector in the board´s housing,o i choose this side.
first you have to solder the GND pins to the rectangular contact on the edge of the board. you can also scratch some of the green paint and get a bigger solder point, since most of this side of the board is GND (i did that later to get more solid mount). note that center pin is in the air, perfectly above the round contact next to the rectangle.
then, you have to gently bend the pin to touch the board. it will touch perfectly over the feed point. apply solder, and make sure there is NO CONTINUITY between outer pins and center pin. if there is not, yo did a good soldering job and your board is ready.
it looks very nice.
and after some modding to the case (opening a bigger hole for the antenna), you have a detachable antenna receiver. i put the 5dBi antenna from the same wifi adapter to get going now, but this opens possibility of testing many antennas to increase range.
By now, the only range test i did, for time reasons, was putting the quad on the rooftop of my car, and walked away in the forest (no line of sight test posibility, i live in a forest....), switching fly modes wit Tx and hearing the change being effective through droid planner telemetry. i walked about 150 meters, and changes to mode were effective immediately, with lots of trees in between, and no line of sight.
i have to do better testing in the field, but looks like it's working fine.
Hope you can make use of this. any questions you have, i will try to answer.