Thanks Peter. Today installed external yagi pointing now to another tower. I was experimenting with the antenna ports a bit. I have 3G contract and SIM card so I assumed that
router should work only with one antenna as only 4G/LTE is mimo??

First, external antenna was connected to the antenna port near DC jack (further port A) and port near sim card (further port B) there was the original stick antenna. Operation was ok, signals 100% and speed 1-5/1.5MB.
Then I changed external antenna to port B and stick to port A. Noticed that when there was nothing connected to port B the signal meter in the router was going to zero.
After plugged in antennas signals were again 100% and speed 1-3/1MB. Then I plugged out the antenna from port A, and noticed that upload speed dropped somewhere near 0.3MB or so.

Put back external antenna in port A and stick in B. This seems to be so far the best solution. Anyway, it seems to be that MR200 uses both antenna ports even in 3G (WDCMA or HSDPA) mode. Now it seems to be that
upload speed is a bit lower than with original sticks on but hopefully the connection is more reliable. After a week we'll see.

Johannes