[G0HZU_JMR]

Yes, it's interesting to see the spread in the frequency across a batch of crystals.

I managed to find a sample bag of 30pF ATC800B caps and the most accurate one on my VNA measured 29.8pF across HF and into VHF.

I must admit I was more than a bit excited when I connected it inline with my lashup test fixture. By changing the FM range on the Mi2024 sig gen it's possible to get a very precise calibration for zero phase on the +/- 6deg range on the HP8405A so it's worth playing with the FM setting on the sig gen to get best results. I also ended up reducing the loop filter cap to 1000uF to speed it up a bit.

I tried the original crystal on the HP8405A test setup and it measured 4.032015MHz with this 30pF loading. On the VNA yesterday the model predicted 4.032025MHz for the same crystal with a perfect 30pF capacitor so the VNA/simulator was within 10Hz and this wasn't bad!