Sir
I made a Variable Frequency Sine Wave Generator that can vary frequency from 90 to 150Hz, its running fine, but the problem is that the noise in sine wave gets pronounced in between the certain frequency band as can be seen in screen # 4, below & above that band there is less distortion, what I should do to suppress that noise???
It's some interference/spurious noise deteriorating the clean sine wave due to following expected factors:-
1,due to yours toggle/push push switch being dirty needs to be cleaned.
2,shielded wires inside needs to be checked.
3,if you provide the diagram,then the same can be checked thoroughly if some oscillator creating the trouble,however you yourself may check the oscillators producing the sine step by step by using the oscilloscope and moreover you should check the +B rail feeding to the circuit,
Regard,