I have just bought a new RPi (my 10th or so...) and this time it is an RPi3B+
When connected by Ethernet cable I get very good network speeds as tested with the Swedish "Bredbandskollen":
Download: 224,220 Mbit/s
Upload: 128,090 Mbit/s
But when I switch to WiFi (pulling the Ethernet cable out) I get very disappointing speed:
Download: 4,417 Mbit/s
Upload: 29,752 Mbit/s
I thought that the WiFi on the 3B+ would have been improved but it seems like it is not at all.
Where is the WiFi antenna located on the board?