Dear Mr Farhan
As about me for several days I was asking for help as I've lost the original soft for scale and control of the Si5351. At last I've find HEX file by KD8CEC and I am happy that it works!( Used XLoader).
But till this time did not find the original file and besides this I am not the Arduino specialist. A lot of words but no FILE and how to load it!
To my mind the R50 feed back of the Q70 should be raised to 820K to raise collector U from 1.8 to 6 V - not to over load it by strong signals.
Problems: great carrier in SSB mode TX, more then modulation speech signal! What is it? to use only in reception mode?
The final 12 MHz filter is too wide and do not have 6/60 dB features, + some out of channel signals! But stii very simple and original transceiver not noisy with good sound! Some raising of the price of something 140-150 will not be too much for it. Best regards to you and your team 73! George UR4CRG/RX3ARG