trimmer related phenomena when tuning my YIG

[john23]

Hello ,I have a very weird phenomena my YIG has a tune input.
When I used LD1084 regulator and one of the resistors was a trimmer even thow i put 10uF capacitors on the output and input .
When i try to tune my voltage going into the YIG the YIG starting to jumps 300MHZ 500MHZ back and forth.
So i suspect the TUNE voltage have jumps of 1V at least.
I suspect that when I changed the trimmer value it created this behavior.
A basic voltage divider get my YIG better stability then this thing.
1.Am i correct in my assumption?
2. Why the trimmer could create such a thing?
3.what could be manual tuning alternative for changing of resistor?
https://www.st.com/resource/en/datasheet/ld1084.pdf

[eutectique]

So i suspect the TUNE voltage have jumps of 1V at least.
1.Am i correct in my assumption?

Do you have an oscilloscope?

[john23]

Hello, Is there a better way manually changing the voltage?
maybe some other type of trimmer to use with a regulator?
Thanks.