[AMSAT-BB] Mode J Filter

I am still having desense on my UHF downlink on the IC-9700.  Antenna is a 30 element M2 CP Yagi with SSB Preamp at the antenna. I have yet to check connections at the end for any problems, but will do so. Connectos are all Type N on system. Is there any better option than the Comet CF-416C diplexer to help or even eliminate the 2M uplink from desensing the 70CM downlink ? I would have to weatherize it to ensure longlife, etc.     Perhaps there is a sealed inline filter that would handle the capability of the  radio which is 75 watts out on 70CM.  Anyone with info pleae share with me. Tnx Jerry    KJ4EU