Yes, you can do that. Try to get hold of a so called "splitter" for the frequency range. Most ham radio two-way splitters for 23cm band will do. A splitter is a sort of T-junction, but one which matches impedance. With such a device you can hook two antennas to one receiver.
A splitter will introduce a slight insertion loss (about 0.5dB max. on a good splitter with N jacks), but that's unavoidable.
Rgds,
Ekki/WiMo