Below is the filter that has been made from old 1500MHz ambulance cavities. 1/4 wave series resonant circuit. The left screws are for matching and the right screw is for tuning. Lots of sawing, tapping, and turning involved with help from Tony's (G1HBD) lathe. It's sturdy enough to handle the 100 watts output power. This is now fitted inside the "final PA" box in series with the antenna feed. This has improved the de-sense on the 2340MHz receiver by removing any noise that the PA generates on the input frequency.

Click here to see the VSWR plot and details