In considering adding a new LPF module to replace teh original on board LPF matrix, it is helpful to remove the audio switching from K3. This reduces RF signal routing on the uBITX board. Many have found the signal routing via K3 causes RF to get into the audio so this represents good practice.
It is suggested that Audio M1 and M2 are tied together at R70, and does not involve Tx/Rx switching them with K3.
Power is Tx/Rx switched to Q70 on v4 boards, and the audio pop modification does the same thing on the v3 board.
The procedure is:
- Remove R70
- Bridge the front pad to the adjacent track
- Cut the adjacent track and short the relay sides of both tracks to ground.