The Nano-VNA is a powerful tool for assessing the characteristics of all types of filters, including crystal bandpass filters.
At the first shed workshop of 2022, Mike ZL1AXG discussed the construction of multiple crystal filters for HF rigs. This included a 12 MHz crystal filter for the Simple SSB 80m rig he is constructing in modular form (and this reflected the fifth presentation on that transceiver construction).
He also revealed a further 12 MHz filter and 2 filters at 4MHz for other planned construction projects. In this workshop, Mike covered crystal selection, design options (including lattice filters in general and Cohn and QER filters) and the challenges of achieving a nice shape and a passband that doesn’t have too much ripple.
He also demonstrated a “universal jig” for use with the nano-VNA and discussed when things go wrong with filters (in this case an LPF, or rather the test set up).