For a few weeks I have been using an X50 5G witha  3 SIM in the UK. I am about 750m from the cellphone tower and my signal strength indoors in the best part of the hosue, varies from about -94db to -99db. With the built in antennas I get around 80mbps down and abot 35mbps up.

I was curious how much better the performance would be if I got an external antenna - so I have just tried a Poynting XPOL 2. This a pretty large directional antenna.

In my first test playing around with the best direction I managed to get a signal strength of -88 to -90. However, while the signal strength is significantly better according to X50 it did not make any noticeable difference to my download speed. Interestingly though it did make a significant difference to my upload speed - that went from 35 mbps to over 50.

I am curious why this antenna would inprove the upload but not the download. Does this simply indicate that I am limited by congestion. (At least at the time I did the test.) Or is there another reason?