about google found VCO-s

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as i didn't use the default transistors i was not able to grasp the ® idea behind this mess	finally it best resembled to a phase shift OSC - what it is with a poor fq. ctrl
not a VCO but a Schmitt Trigger

. . . the response speed and frequency range define the possible target app.-s . . . as in fact what i did here was the opposing -- an attempt to find out best range for operation by VCO type (for the ones that didn't work from scratch . . .)

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[Eop]

theoretical wall ~AC line detector

since there is reason to believe the ®´s j-fet input stage rather attenuates than amplifies
the E - field variations i set up a simple band-pass based 1 ::

  

this might still require extra input stage (for deep buried wires)

+ experiment with the layout , sensor , 3-sholds´ sensitivities before we can say if it´s for any good

updated an old Sq.-wave oscillator to a voltage controlled one -
to be mixed with prev. ~50Hz output ::

 

it is good to pre-test and choose + adj. the optos to the same transfer ratio ,

everything else shouldn´t be too much trouble ?

[Eop]