[Elecraft] APF (audio peaking filter) on the K3/K3S/KX3

[Brian Hunt]

The technique I'm using with the APF also involves NR like so:

On an uncrowded band, set the DSP BW to 700 to 1000 Hz. If you have a roofing filter in that range stay within it. 

Turn on NR set to mF5-3 or there about. The wide BW helps the NR work well. The "mix" mode lets a little unprocessed signal+noise through. This is a good weak signal search mode. 

When you find a signal you want to copy, turn on APF and peak it in the filter. Fine tuning helps. There is little ringing because NR has reduced the noise amplitude. You can decrease the DSP BW a little but the NR is more effective with uncorrelated noise. 

This technique has gotten me many pelts in the QRP Fox Hunts. 

73,
Brian, K0DTJ