Insufficient Input and Output Filtering

As hams, we know that equipment needs good input and output filtering to prevent RF from coming in on input and output wiring. Beginning in the 1950's, hams operating the HF bands were deluged with TVI complaints because television manufacturers failed to include high pass filters in their sets. Likewise, audio equipment needs good low pass filtering to reject our signals. Many myopic designers of "high futility" audio gear (and even some professional gear) don't include low pass filters because they don't want to degrade the phase response of the audio path. While good phase response is certainly important, so is RF rejection. Good engineering can satisfy both needs without compromise. Ever since those early days, hams have always assumed that a good low pass filter will kill RFI in audio systems, and a good high pass filter will kill interference to FM and TV. Unfortunately, while good filtering is important, other mechanisms are far more important in most real world situations.



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