Hi Zout,
I found a GW more nearby and tested my proof of concept hardware using this GW.
Sending data works fine and appear in the TTN API.
Found some interesting issues I don't comprehent right know (no receiving a ACK, no OTA join working etc). But first tests looks OK for now, I wil dive into the matter later.
Next bullet on the list is getting our own GW active (covering South/East part of Groningen).