[Elecraft] K-3 Roofing filter comment

[Geoffrey Mackenzie-Kennedy]

Dave,

The sampling point for the K3's hardware AGC is before the DSP in the signal 
path, so unfortunately the DSP filter does not protect the HAGC. The roofing 
filters protect the HAGC.

There is another design approach to eliminating AGC pumping problems, but 
that is another story :-)

73,
Geoff
GM4ESD


On July 12, 2011 at  21:21 Z,  Dave Hachadorian wrote:

> I think one of the Elecraft folks stated on the reflector that
> the -60dB BW of the DSP is (-6dB BW + 300Hz).
>
> So at DSP BW = 2800 Hz,
> BW60 = 3100 Hz.
> Equivalent shape factor would be 3100/2800 = 1.1
> That's pretty doggone steep.
> Any reasonable amplitude signal (not triggering hardware AGC)
> over 1550 Hz off center would be down 60 dB.
>
> I think I've got that straight. Comments welcome.
>
> Dave Hachadorian, K6LL
> Big Bear Lake, CA