Originally Posted by blueangel-eric
commercial companies such as Sinclair has stuff though they are so expensive a home user probably won't afford one. The railroads use those as they have different radios on different channels fed to the same antennas on the towers. It seems they're for a specific band though not multiband.
Your link goes to a transmitter combiner, which would do no good at all for receiving. The OP clearly states that he needs "both radios to RX at the same time."
A simple splitter would do that job nicely.
BTW, there ARE combiners out there that allow both transmit AND receive operation for multiple radios on a single antenna. They're specifically designed for places like dispatch centers where multiple control stations might exist. I doubt most of us could afford the several thousands of dollars they cost.