[amsat-bb] Question about duplexer as a high-pass filter

My satellite rig is two HTs running to an Arrow antenna. Trying my best to operate full duplex. When operating V/U I am using the UHF side of the Arrow duplexer as a high pass filter between the UHF antenna feed point and the UHF HT to keep the 2 m transmit signal from desensing the UHF receive.

But it only sort of works.

This set up leaves the VHF end of the duplexer open and just hanging. Would this setup work better with a 50 ohm load across that empty connection? (Sorry if this is a dumb or elementary question, but I'll never find out if I don't ask.)

All helpful insights are welcome.

Steve AI9IN