[Elecraft] Need to shift 8 pole 2.1 filter?

[Don Wilhelm]

  You apparently are changing the filter width with the WIDTH control - 
which moves both the high and low end of the filter width, so it cuts 
out a good part of the lows in the SSB received signal.  To get those 
lows back, you must use the SHIFT.

To make things easier, switch to the LO-CUT-HI selection and reduce the 
width using only the HI - cut knob.  You will not have to adjust 
anything else to make the voice recognizable and intelligible because 
the lows in the voice are retained.

Further explanation - when you change the width from 2.8 to 2.1, you 
reduce the width by 700 Hz, and that is 350 Hz from both the high end 
and the low end.  If you started with an audio passband of 200 Hz to 
3000 Hz, the resulting passband after the width reduction is 550 Hz to 
2450 Hz - that is too much reduction of the lows to be intelligible, so 
you have to shift downward by 350 Hz to make it intelligible again, and 
with a passband from 200 Hz to 2300 Hz.

73,
Don W3FPR

On 4/14/2011 2:44 PM, kcflyers wrote:
> My K3 has 2.8 and 2.1 8 pole filters in both main and sub receivers.  Set up
> for zero offset per manual.  When I switch to 2.1 filter, I need to use the
> Shift control to make receive audio sound approx normal.  Perhaps 3/4 khz
> shift.  Is this normal?  When using the 2.8 filters, no shift is needed.
>
>