Is that like a Ghost to Ghost Broadcast? (Thank you Abbott and Costello). It is assur to do this in the sense that there are “mediums” who claim to. And the Torah doesn’t say they are unable to speak with the dead, just that it is assur for us to go to them. Just like with ham, l’havdil, efshi v’efshi, aval lo muttar.
Personally, I cannot say with certitude that these people who claim to channel the dead cannot fo what they claim. I believe most of them are phony. But I have had experiences myself since my parents were niftar, that defy conventional wisdom and logic I would never go to a medium to try to get a message from the, even if I thought that person had the capability of doing so