Finally I modified my little TwinTalker 3600. I had to do it because my first PMR446, the used TwinTalker 3500, suffered deafness and its output was less than 200 milliwatt.
In place of the original antenna (the spring), I welded a SMA connector and a BNC adaptor.
I used a SMA connector because this radio has very microscopic dimensions. Plus, because the TwinTalker 3600 was opened, I lightly increased the modulation of this radio that was a little bit weak.
Below the TwinTalker 3600 with SMA only and with SMA-BNC ready to link to an external antenna.
Here is my little TwinTalker 3600 opened on the surgery table and ready to be hacked with a SMA connector.
The spring antenna, the cover and the SMA connector ready to be nested.
The rear and front PCB of my little TwinTalker 3600.
Finally the soldering photos. Remember always to solder the connector's ground, in the nearest point where we withdraw the antenna's signal.