Broadcast band receiver mod is on hold

I kept the idea of making the SSB receiver by modifying a broadcast band receiver on hold for now.  Initial testing shows unacceptable levels of noise from the radio circuit and the frequency instability in the built in tuner. The tuner jumps few hundred kHz per second. To make anything useful first of all the tuner must be re wired to some crystal based or PLL based tuner. I will try to do the tuner modification first when I manage some time.

Design Of A Code practice OSC

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

Relay driver using a vacuum tube

This project uses a vacuum tube in a relay driver circuit. Actually the tube makes the circuit complex and a relay driver can be many times simpler than that, but my target was to use the vacuum tube and to demonstrate that a vacuum tube can be used in low voltage circuit and can be used to drive a relay, though the presence of vacuum tube makes unnecessarily complex. Main moto of this experiment to have fun. Relay is energized when S2 is turned on. The circuit diagram is taken directly from my notebook page so it is not properly edited. I could not find some time to make proper nice looking  drawing in Kicad.This circuit was tested in a breadboard.