How to Adjust the TCXO to be on Frequency
Adjustment should not be needed as they are set to within 0.5 Hz, but if you really want to adjust them, here are the steps to adjust the TXCXO using the multiturn pot. The pot has some backlash, so follow the instructions below to set it precisely.
Adjust the pot to get the frequency to somewhere close to where you want.
Turn the pot about +/- one or two rotations around the setting a few times to clean the wiper.
Adjust the pot CCW below the desired frequency by a few Hz.
Slowly turn the pot CW, a little bit at a time until you get to where you want it set. If you overshoot, repeat from step 1.
It has to be adjusted to where you want in one direction only. It may work better to adjust CW in step 3 and CCW in step 4.
I usually tweak it very slightly, then wait 30 seconds to see where the frequency winds up. It will take a few minutes, but I can generally get it within .3 Hz. After that it may move 1 Hz with temperature and time, but I have not had them long enough to know for sure. Recent tests of production units has shown less than 0.5 Hz drift.
Turning it upside down may cause a couple tenths of a Hz change also.
Updated September 7, 2017