[Elecraft] K3 2.7kHz filter DSP FC

[Bruce Beford]

Stewart wrote:

> Can someone explain to me why with the standard 5 Pole 2.7 kHz 
> filter the DSP FC = 1.6kHz ?
> 
> Looking at the NORMed DSP for that filter the LO = 0.25 kHz and 
> the HI = 2.7 kHz.
> 
> So I would have thought that FC = (2.7 - 0.25) / 2 or 1.225 kHz 
> say 1.2 kHz.

> Maybe my idea of what FC represents is wrong..

> 73
> Stewart G3RXQ

Stewart, (put simply)

If the center frequency was set to 1.225 KHz (or close) as you suggest, then
the 2.7 KHz filter would let though too much opposite-sideband energy. We
want some stopping power down close to zero Hertz, so the filter edge is
kept 250 Hz above zero.

Ya?

-Bruce N1RX