Hi Paul
Great to hear that you have completed a scratch build of my MKll BitX multi-band transceiver.
I have not seen or experienced the chirp you mentioned when going from RX to TX so I suspect the problem is associated with the TDA2003 amplifier stage.
As standard the MKll multi-band exciter has an LM380-8 as the final audio output stage and I chose this as my experiences with the LM386 have not been great!
Both the original BitX and my multi-band effort do suffer with speaker "thud" when going from RX to TX, in my circuit Q11 in the audio stage does help reduce the thud to an acceptable level but there is still room for improvement and one day I may look at this again.
When working correctly with everything aligned the receive performance is excellent considering its simplicity. The AGC makes a huge difference over the standard BitX without an AGC and the transmit audio is greatly improved with the op-amp and its associated filtering.
Keep us posted on your progress and it is great to hear that you are enjoying the project.
Regards & 73
Andy de G6LBQ
