I have just started to learn CW and realized that a code practice OSCILLATOR is very useful. Using simple 555 astable oscillator was initial idea but it generates square wave and not pleasant to hear. I took help from my ham friend VU3BMT and he suggested a modified version of twin T oscillator originally introduced at k4icy CPO and more information at Twin-T Audio Oscillator, here and here. I build the version modified by VU3BMT and here is the drawing from his notebook
This design worked remarkably nice. Clean Sine wave from Oscillator in the first power up attempt, but since I did not have the transistors 2N4403 2N4401 and 2N7000 so I used 2N3904 2N3906 and BS170. Replacing transistor did not seem to alter circuit performance. My circuit looks like below
Output from oscillator only without final power amplifier
Construction in Manhattan style
Test of frequency and gain of power amplifier
No comments:
Post a Comment