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locked EMRFD Oscillator Problem #off_topic #oscillator #emrfd

ashok.das81@...
 

Hi all experts,

I am trying to use the oscillator described in EMRFD book page 4.9 fig 4.13 C. I have attached a drawing here. Sorry for the bad drawing. The values inside the brackets are actual values that I have used in my circuit.


Now the problems are

1) Whenever I bring my hand near to oscillator its frequency changes considerably. This is very annoying. How to stop that ? I know this is due to capacitance of my body, but there must be some way to stop this as professional designs does not behave like this. There must be some standard way to stop this. I have made the circuit in Manhattan Style.

2) I don't understand how to take output from this oscillator. I tried two points marked A and B in circuit. If I take O/P from A the it shows harmonics as seen from my scope pic . How to stop this harmonics?


3) If I take O/P from B then it looks OK but frequency again changes considerably. So How to take O/P from this oscillator ?


Also I need suggestion about a buffer amplifier for this oscillator, preferably BJT based as JFET are very scarce in my country.

Thanks & Regards
Ashok Das