A LoRaWAN gateway shouldn’t transmit unless commanded to do so by a network server.
Typically this would happen because:
- It received a node transmission to which the network server wanted to reply
- The network server is configured to use the gateway as part of a network operated in a mode with unsolicited beacons
- The network server sends gateway-to-gateway “pings” for mapping or diagnostic purposes
- The gateway software itself has some non-standard diagnostic transmission
Operating a gateway in transmit mode without an antenna connected is outside of stress limits; that said, it’s typically not instantly fatal. Having the u.fl connector pop off the card is naturally something that happens to people, it should be avoided, but…
Something you could consider would be buying a low power dummy load with the appropriate connector to keep in your workspace (basically just a resistor packaged in a way that’s geometrically clean to a GHz; an inline attenuator >10dB will come suitably close, too, even with the other port improperly left open). That’s not really a bad idea for close in setup anyway; you’ll leak enough power to talk to nodes sitting on the bench, and you might avoid overloading things in the way that tends to happen if you have things so close with actual antennas. Or just get a basic antenna to use… or put an antenna on the roof and run the cable to your bench…