[osmocom-analog] Help with cable connection from the phone to the SDR.

Hello, I have been wanting to build a TACS base station with Osmocom analog for a while now, and have decided finally to do it! To avoid regulations, I would like to do it over a cabled connection from the phone to the SDR. I have read that some form of load or attenuators are needed to stop the phone and SDR frying themselves. Unfortunately I have little knowledge on this subject, so I wondered if anyone here can tell be what sort of load I need.

Any help would be greatly appreciated