The entire purpose of a duplexer is to be able to use a single antenna to transmit and receive at the same time. However, in a mobile situation 2 antennas are easy, allowing a low power duplexer to be used to create a highly functional, vhf inband vehicular repeater. High power transmitters generally require high priced duplexers, and you still lose some power for the trouble. In this configuration all the transmit power goes to the antenna.
In this video I show the connection details and a demonstration of the repeater in use.
Update! 8-25-24
I noticed significant desense if I transmitted low and received high using the mobile duplexer and no desense if I transmitted high and received low. This led me to the issue of near-field rf emissions. Please refer to this video where I address that.
https://www.youtube.com/watch?v=IeXRjqoABgk