DRO tuning screw strange behaviour

As i know, frequency of DRO must increase if distance between screw and DR decreases.
But I am observing decrease, and then some increase of frequency while turning screw clockwise (distance decreases). Original DRO enclosure was without tuning screw, i added hole and aluminium screw on top of DR.

When you lower a tuning screw to the top of a dielectric puck, you are capacitively loading it. The same way as if you squirted some glue on the top of the dielectric puck lowers the frequency, moving the screw closer will lower the resonant frequency.

Thank for your reply! Yesterday i was reading http://www.4timing.com/technical_considerations.htm, and in "4. Mechanical Consideration" i can't understand this phrase:
Here: http://www.satelliteguys.us/xen/thre...art-one.30837/
So here we lower frequency by decreasing spacing between DRO and screw.
Tuning screw too close = lower frequency.

But here:tmo.jpl.nasa.gov/progress_report/42-162/162C.pdf
So here we increase frequency by decreasing spacing between DRO and screw.
Tuning screw too close = higher frequency.

I do not get something here....

Also just found this:
http://www.atva.com.ar/frecuencias/1...b_blue_cup.pdf
Tuning screw too close = higher frequency...

In most of the applications the DRO is inside of a cavity and the screw mechanism is used to alter the cavity oscillation resonant frequency.
When a metal wall of the resonant cavity is moved toward the interior, the resonant frequency will decrease if the stored energy is mainly in electric field.
When the stored energy close to the cavity walls is mostly magnetic, as in the case of shielded dielectric resonators, the resonant frequency will increase when the metal wall move toward the interior.

Any good online information about DRO enclosure design? I found rule of thumb: enclosure must be more than three pucks in width and height: http://www.cel.com/pdf/appnotes/an1035.pdf
And some info on this page: http://www.trans-techinc.com/product...ric-Resonators

I can see that the discutees never saw a real DRO. Tuning by a conductive round screw head really should increase the DRO frequency when the head closes to the dielectric puck.But when it goes farther away, the frequency may increase with distance.
Make sure the cavity does not resonate close to DRO frequency, otherwise you have two coupled resonators in action.