Hi guys,

believe it or not - I have found a source describing how an inductance can be made variable as Stan Meyer describes in his circuit diagrams.

http://forum.allaboutcircuits.com/showpost.php?p=56993&postcount=1

to adjust a windings inductance wire it bifilar like a transformer and use the primary as your inductance in charge.

in the secondary windings there is a potentiometer. adjusting the pot makes primary inductance change!!!

enjoy.

Thanks for sharing.
I use a ferrite core for adjusting (air wound) inductances, works like a charm.
The only hassle about it is that you have to lower (or raise) the core by hand everytime you want to tune the inductance.
But if it's supposed to be part of a PLL circuit then your solution would be the preferred method of course, otherwise I
would for instance have to use some stepper motor arrangement in order to get the job done lowering/raising the core in
order to meet the command value from the PLL circuit.

It is true if we use separate cores for each choke otherwise inductance of every winding will change.
Can be a test setup though.