One of the cool CW features that I discovered this summer on my KX3 is audio peak filtering. Somehow, turning this on, brings a signal right up out of the mud. This feature is available on a number of mid-level and high-level rigs, such as the K3, IC-7610, FT DX 1200, and my new (to me) Flex 6400. Unfortunately, it’s not available on the IC-7300, even though I’m pretty sure that it’s all done digitally now and should be relatively easy to implement.
It really does work well. Here’s a video demonstrating how the Flex Radio APF:
In the CW mode, the APF (Audio Peak Filter) function has an audio peak at the signal frequency; this improves the S/N and increases the readability of the CW signal. The APF peak frequency can be finely aligned.
It works so well that I always have it on when operating CW. I want more details on how it works, though. I wouldn’t think that it’s just a simple audio filter. If anyone can point me to a more detailed explanation of how audio peak filtering works, I’d appreciate it.