1. Relay is not used in Rf Circuits its for Dc and low freq Ac circuits.

2.In my openion the only solution is the Antenna Switch. Plz search for proper Antenna Switch.

3.The option you want to avail "To tie up both the Tx and Rx" is quite dangerous for your Reciever front end provided you are sure that your reciver will be shut down before the transmission starts and will never come on till the Tx is active.

4. Here is the list of Antenna Switches, you may select according to your requirement.

http://www.macom.com/psc/jsp/L...itches.txt