[amsat-bb] 2-to-1 spliiter with DC pass?

I have an Icom 910, the preamp control is very convenient for turning on masthead preamps. I also have an Icom R8500 comm receiver and I would like to do a little hacking with the 10.7MHz IF output of the R8500 using the same antenna feed as the IC-910.

So, is there a 2-1 splitter available that will pass DC from the 910 to the antenna but not to the other receiver? Also some sort of arrangement that doesn't blow up the R8500 would be kind of nice in case I accidentally key the 910 transmitter.

thanks, jeff AD6EO