[Elecraft] Roofing filters and DSP bandwidth tuning

[Fred Jensen]

NJ Mike:  If I understand your question, the answer is "Yes, as you 
narrow the DSP BW with the 'WIDTH" knob, the roofing filters will switch 
such that the narrowest filter that still includes the DSP BW will be 
selected".

To your second question, the ultimate BW is set by the DSP, and on my 
K3, that's 50 Hz.  It doesn't really matter what roofing filter is 
selected.  The xtal filters are in the 1st IF [8 MHz] and their primary 
[maybe only] purpose is to suppress strong signals outside the DSP BW 
that would activate the AGC and affect the level of the desired signal 
inside the DSP BW, even though you can't hear them.  It follows that 
you'd probably like the selection of roofing filters to follow the DSP 
BW as closely as possible.  You won't see any difference between your 
Rigs A, B, and C.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
> NJ Mike wrote:
>
> If I understand it correctly, as you turn the bandwidth knob
> counterclockwise, the filter narrows.  At some point, it hits the next
> roofing filter and then....narrows more?  Just trying to understand so 
> I can
> get the right filters.  Rig A (below) is what Elecraft recommends for my
> operating profile.
>
> What would be the difference between the following three examples, as 
> far as
> how narrow the bandwidth could actually be adjusted?
>
> Rig A with 2.8, 2.1, 400, 250, 200 filters
> Rig B with 2.8, 2.1, 400, 250 filters
> Rig C with 2.8, 2.1, 400, 200 filters