Hello,
is there a way to connect external 4G/LTE antenna using pigtail SMA?
Whitch antenna connections to use?
Thanks for advise.
Martynas
Check if you can find your model or a similar one in confused bird forum:
https://confusedbird.com/thread-119.html
as there may be additional notes/info, but the two antenna connectors for LTE are those with yellow and red wires on top right of your image, connected to the "bolted on" modem, which is (should be) a R11e-LTE7:
https://mikrotik.com/product/r11e_lte7
Connectors are 2 uUFL.
Thank you for the reply. I reviewed the provided link from the Confused Bird forum, but it mentions older models.
Your response is very logical, and I completely agree with it 
What puzzles me is that the router uses the original antennas only for the Wi-Fi connection—meaning only the black and gray wires on the left go to the antennas.
I've ordered the pigtail (https://mikrotik.com/product/acsmaufl) and am waiting for it to arrive. I'll get back to you with an update as soon as I test it.
Did you look at all pages ?
Here is the latest 5G R17
What Is puzzling?
The device has internal LTE antennas and external wifi ones.
If you follow the yellow and red cables, likely on the other end there are two clover-like PCB antennas similar to:
https://confusedbird.com/thread-119-post-3083.html#pid3083