Improve 4G

Signal strength is only one important factor of many. With a strength very much weaker than yours, I've got 100mbps before on EE. However, to do this you need a very good signal quality and a mast with lots of resource blocks (few users and lots of spectrum) as well as good backhaul etc. 3's LTE is currently 2x15MHz L18 which allows for a technical maximum of around 120mbps. (Yes, I know they have 800MHz, but is only 2x5MHz for a maximum of about 37mbps and setup very much as a last resort). Theoretical maximum speeds are based on current modulation and MIMO schemes used, as well as other variables.

As a result of these things, you are well advised to try pointing the antenna at all the masts you have line of site to because from other/further masts the signal may well be very, very much faster, even if it is weaker.

So in theory I should try to connect to the best mast that provides me LTE Band 3, right?

Yep. Try each mast in turn and test the speed.

Pedroc,

I stand corrected on use of X-Pol in the UK, have been mainly focused on Asia in the last couple of years.

Re the term 'mast' or 'masts' technically unless they have guy ropes (eg Membury Services, 500' mast) they are all towers. It is unfortunate that that the media and public have latched on mast for everything from a 10mtr monopole upwards.