Scott, I have one v1.1 board and I am looking into this thread to understand the problem and the approach you did to fix the issues with v1.2 and I am wondering why you did not simply change the input signal from P3 (AFIN) to P9 (SPO) of CN2, not adding duplicated additional filter on T2-135 board.
According to DR-135 service manual, P9 (SPO) is called as VLI and it provides 1200bps decoding signal with 300mV. It is actually pin 4 of DR-135 D-SUB connector for external TNC connection. I am happy to hear your explanation to improve my v1.1 board receiver performance when I use it. Regards, take de JA5AEA
