SF12 for activation

Hi,

The TTN-gateway that I use is hardly "visible" from my MKR WAN 1300 sitting where it sits.

Looking at the logs of TTN, I can see that activations (joinOTAA(...)) are always performed with SF7 while upling/downlink messages are then exchanged with SF12.

Is there a way to force activations to use SF12 from my side (the MKR WAN 1300)?

Tried dataRate(0) before executing the joinOTAA(...) function, but that leads to an immediate error when calling joinOTAA.

Thanks,
M.