[Elecraft] Crystal Filter Offset in 4.81, What does it mean?

[Lyle Johnson]

The "center of the passband to the nominal pitch value" only occurs at 
higher pitches and/or narrower passbands.

Think about the case where you have 1.5 kHz width selected and a pitch 
of 500 Hz.  You defintely do NOT want the center of the filter and the 
pitch to be equal,or you'd have terrible opposite sideband suppression.

The calculations done internally in the K3 to adjust the IF and AF 
passbands based on the settings of center frequency, width and pitch are 
fairly complex.

"Zero beat" has to do with frequencies, not filter responses, and 
changing the filter edge should have no practical effect on whether or 
not you are zero beat.  I say practical because the calculations done 
inside the radio coupled with finite resolution of the various 
oscillators may result in a 1 or 2 Hz difference, and someone is bound 
to measure this :-)

Finally, the new offsets apply to receive only. They have zero effect on 
how the radio is configured on transmit.

73,

Lyle KK7P
> ...
>
> It appears if you do this, you might also have to adjust the filter 
> offset to bring the center of the passband back to the nominal pitch 
> value.
> ...
>> I installed the 4.81 beta firmware and I am able to change the 
>> crystal filter
>> offset as described in the firmware notes... Previous to this release 
>> I would have assumed that the crystal
>> filter is centered on my chosen CW pitch suggesting a 0 KHz offset. If I
>> choose one of the 3 offsets am I now listening (and transmitting) 
>> slightly
>> off zero beat...