hi there
thats not really a "small" project, rather a relatively complex transceiver project
If you really wanted a small relatively easy transmitter project how about building a couple of FM bug transmitters
they could then both have small FM broadcast band receivers and have 2 way comms
dont know what country you are in, how about updating your profile so we can see that
maybe in your country you have electronics hobbyist shops that sell kitsets for FM transmitters like we do in Australia and USA