Interdigital Filters - remade

I etched the new boards over the weekend. The frequency of the 738 and 571 filters came out spot on. The pesky "step" is still there especially on the 571 filter. The loss is less on the 571 but that was expected per the simulation using FR4 board stock. The return loss just sucked on both. I ended up adding a surface mount trimmer cap (3 to 12 pf I think) in series with the input on the 571 filter. I also moved the input tap up several millimeters. About as far as I could reach with the body of the trimmer. Adjusting the cap I was able to achieve a return loss of 18 DB. Slightly above the desired frequency I could get 20. I adjusted for best RL on the design frequency. When I get some time I will add the same capacitor to the 738 MHz filter. For now these are done and I will go on to other modules of the project.