I've decided I want to make an SSB, along the lines of the BitX or something. Along those lines, I decided I should make a crystal filter for use in it. I'll be following the directions from W7ZOI.
First, I ordered a lot of 100 9MHz crystals off of Aliexpress:
I plan to match them using the NanoVNA. The Windows software for that has instructions on making a test jig (basically 4:1 matching transformers and 3db pads on either side of the crystal) and apparently has a mode to let you match crystals in batch. But I got impatient and wanted to see what it would look like to just make one with the first four crystals I pulled. The result is here
The best I can tell, it is centered at 8.9978MHz with a 1.8KHz bandwidth (to the -3dB point), with a 2.48dB insertion loss. Which isn't far off what I want (was aiming for a 2KHz bandwidth). So all in all, a pretty good result I think? I want to try again with NanoVNA Saver when I get a chance (to get better numbers/pictures) and I really should actually calibrate it :) But it was a quick test when I had a few minutes between things.
Edit: Got NanoVNA going, and calibrated. I was pretty spot on before.
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