sudo apt-get update
sudo apt-get install build-essential linux-headers-generic
wget https://github.com/lwfinger/rtlwifi_new/archive/test.zip
unzip test.zip
cd rtlwifi_new-test
make
sudo make install

Now reboot and test:
Code:

sudo modprobe -rv rtl8723be
sudo modprobe -v rtl8723be ant_sel=1

Test the results. Then

Code:

sudo modprobe -rv rtl8723be
sudo modprobe -v rtl8723be ant_sel=2