Charles & Sandra Cohen
All the previous ideas are fine. But I have a question:
. . . Why do you want to adjust it?
In actual use, you'll be tuning to someone else's transmitted signal, except for the "JTxxxx" modes. And for those modes, you just need enough accuracy to be within the appropriate sub-band - that's a few kHz wide.
For PSK31, "drift" matters. But absolute RF frequency accuracy is irrelevant.
. Charles VA7CPC