When the design was ready I ordered a set of prototype PCB's and after 1.5 weeks they got delivered.
And because i don't know what the output power is of my NanoVNA's and other people use big boy toys, I think it's a good idea to add them. Also I added 2 attenuation sections because in the document Simplified Tools and Methods for Measuring Crystals, Jim Kortge, K8IQY states that crystal under test should not be driven at a level higher than aprx -10 dBm.
Just like like my QRP-Labs filter adapter for NanoVNA, it has build in calibrations support to get the maximum out of it. With this new information and experience with the the improvised adapter and plans to build a new SSB rig which includes a few crystal filters (SSB, CW in 2 band widths), I designed a crystal test adapter for the NanoVNA or any other VNA / spectrum analyzer. So using the 4:1 bifilar wound FT37-43 seems to be a good improvement and although the NanoVNA and the NanoVNA H4 don't have super dynamic range it gives a lot of information about the crystal. Little loss on the first peak but more depth in the bottom. Looking at the same 16MHz crystal with my NanoVNA-H4 i found out that it's showing a much better detailed and deeper response. A small improvementīased on that information I made another improvised adapter using 4:1 bifilar wound FT37-43 cores. This can be done by using a PI resistor network or by using a 4:1 bifilar transformer. In general a matching network from 50 ohm to 12.5 ohm and back is used to get the best match. Smith K8ZOA (see above), shownotes can be downloaded.
Crystal Motional Parameters A Comparison of Measurement Approaches - Jack R.Technical Introduction Crystals - Corning Frequency Control Inc (PDF) - points out IEC444-1 and 2.Looking for more information on measuring crystals I found a few technical PDF's and websites about crystal testing : Looking at one 16MHz crystal out of a batch of 10. Most of the time I buy a large bulk of crystal from the same frequency and measure the response of the individual crystal with a improvised adapter which plugs into my QRP-Labs filter adapter for NanoVNA. Crystal Measuring Adapter (CMA) for NanoVNAĪs a hamradio homebrewer I often use crystals as a frequency source or for building of crystal filters.
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