I have two vhf antennas on a Nmo, roof mounted. I would like to connect both to single scanner, is that a waste of an antenna when I could use it on a second scanner ?
Waste of antenna. You'll get all kinds of nulls that will effect your omnidirectional signal, not to mention a impedance mismatch. Use it for a second scanner or cap it off
I agree with the other post to not do it. But try it with similar antennas and two different ones and see what you experience. Gain the personal knowledge through experimenting.
The only thing your out is a BNC tee.