metal detector problem

[jtjohnsontellis]

dear sir
im extremely happy with all the help that you are providing to students like us
im a student of 1st yea engg and i need the metal detector circuit that u have mentioned in ur site for ma project.but it seem to encounter some problem wich i cant recognize.when i connect the speaker i can hear the noise tat is amplified and continues to remain the same even if the trimmer is tuned,i really need ur suggestion 4 this
plz help.thak u
johnson
9738610416
india
http://www.next.gr/inside-circuits/meta ... l6642.html
plz check and suggest me wat changes i can do to make it work properly..thank you

[pebe]

What do you mean by 'noise'? Is it random noise or an audio tone?

[jtjohnsontellis]

noise in the sense i get output in the speaker even when the meatl s not closer by.the circuit was suppose to give zero signals as output wen the metal is not near by(superheterodyne principle)but in this case it gives an output...even if the variable capacitance is tuned it doesnot make any difference.so i request u if u can suggest me some other circuit which is really efficient or suggest any changes in this circuit./
thank u very much 4 ur valuable replies
thank u
johnson

[pebe]

You haven't answered the question so it's not easy to diagnose the problem.

Again, What kind of noise is it? Does it sound like a hiss, or more like a clean note as when a flute is played? And can its level be varied with the volume control?