The ethernet dummload
To lower the risk of interfering with a commercial network operator you should operate your BS11 with a dummyload. We discovered that an old ethernet terminator can do the job. It is just a 50Ohms resistor - exactly what we need.
To connect the terminator to the BS11 you need an N-Connector to BNC adaptor. Just put them together and you have a nice dummyload for your BTS.
We have tested the dummyload for a while. It worked great. We had coverage in the laboratory-room but nothing came out. Even our spectrum analyser did not show up any measureable singals when it was moved outside the room. But unfortunately this does not solve the problem that the telephones are still transmitting signals that could interfere with the commercial networks.