design a crystal oscillator

It could work (and a notch may help clean up) but -70dB seem pretty average close in phase noise? Not that it really made too much difference getting to -100dB, the power supply had more impact so what will you feed these with?
 
I want to verify if the method in [1] can help to obtain a better result. -70dBC is the original one. Battery is used the same as that in [1].
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You could take a note out of Jim William's application notes in reducing noise - at the moment it's not shielded.

I do wonder if you have two battery packs if the battery noise isn't cancelled out compared to a centre tapped 12V battery.