[Elecraft] Using CWT to determine 8-pole CW filter offsets (was: Shift pitch)

[ni0c]

On 27 Jan., W5UN wrote:

"I have three 8 pole filters installed, 2.8, 1.8, and .4 kHz. As I 
rotate the WIDTH knob, the filters switch in and out at their 
transition frequencies (as they should). But when that switch occurs, 
the background noise pitch frequency seems to jump to a different 
SHIFT frequency setting.  In other words, the transition between 
filters is not smooth.

I am wondering if all K3's with 8 pole filters do the same thing as mine?

My filter offsets are all set to zero, as that is what I am told the 
8 pole filters offsets should be."


I've noticed the same thing happening when transitioning 
from the 250 Hz 8-pole filter to the 200 Hz 5-pole.  This 
morning, I noticed the CWT was a couple of notches to 
the left of center whenever the receiver was tuned to an
unoccupied frequency with the 8-pole filter.  (It was on
dead center with the other filters.)  

I then used the Elecraft K3 Utility to experiment with 
various offset numbers for the 8-pole filter. It only took 
a handful of trials before I came up with a setting of 
-0.09 that resulted in CWT being centered on noise 
and a satisfactory transition with the 5-pole filter.

Thanks to Elecraft for the MCU 2.80 firmware that 
allows the CWT to remain on all the time.

BTW, I really like AA6YQ's DXLab Commander program
for controlling the K3.  Among other nice features. it has
a convenient slide bar for adjusting the DSP width and shift.

73,
Chuck Guenther  NI0C
K2/10 s/n 5853
K3/100 s/n 1061       

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/elecraft/attachments/20090207/804fa262/attachment.html