Here 3 RTK Surveyin duration inconsistency

Hello, I have been trying on an implemantation of px4 gps driver to use with here+. During the testing of it I noticed that surveyin times varies greatly.

First I suspected nearby metal objects might be the cause. I started testing on the roof. And yesterday it took ~10 minutes for 2m accuracy but today it took more than a hour for it to reach ~7m accuracy, at the same place, with same hardware software etc.

To eliminate the possibility of implementation difference I trid with mission planner and qground as well.

I am probably doing something wrong as the docs says “to achieve the absolute accuracy of 2m takes a few minutes” but I have never be able to reach it.

Is this normal? What should I look for debugging this issue? Any suggestions for tests? What could be the affecting factors (heat? twists in cable that connects base antena to base?) ?

In addition to my question, some times I notice surveyin accuracy goes up. Is that normal?

Also is there away for me to test the behaviour of here+ rtk directly, or with ucenter?