Thank you Alan. I've attached an image of the whole setup including the filter, the test rig and the VNA. Please note that I'm just using hookup wire to connect the filter to the testing rig--no SMA or BNC connectors. It made no visible difference when testing on the scope using the wires or direct to a leg of the input and output capacitors. The other image is with a wire connecting the input to the output of the test right. The result is 0db flat across the range for S21. The signal generator has 50 ohm output impedance, and the scope has a very high impedance input. Not sure about the VNA. I tried the setup with a 50 ohm resistor to ground on the filter output and found no difference in the VNA behavior. Thanks for your help. 73, Mitch NK3H
