[Elecraft] K3 APF (audio peaking filter) progress report #2

[Lyle Johnson]

Paul,

The Yaesu hardware-based APF design resulted in essentially constant 
bandwidth of about 30 Hz (6 dB points) and a peaking gain from 7.5 dB to 
10 dB  depending on its peaking frequency (200 Hz to 1 kHz).

The present K3 APF we're testing has a constant bandwidth of 30 Hz at 
the 6 dB points and constant 9 dB of peaking gain. It is an IIR filter, 
closely mimicking a hardware approach.

73,

Lyle KK7P

> I believe the FT-1000/D's APF had a minimum Q of 10 at the lowest F setting,
> then progressively increased to about 30 at the highest setting.