[Elecraft] Filter question

[David A. Belsley]

Stan:
   This behavior is typical.  I don't have actual figures, but I would 
bet that the majority of K2s display this issue.  It is not really a 
problem, and there is a sense in which you can't get rid of it.  You 
might be able to get it to behave for a while, but in time it will 
return.  It has to do with the fact that the K2's frequency resolution 
is only within 10-20 Hz, so what you are hearing is within spec.

   You might try the following to see if it clears up, at least for a 
while.  After you get your BFO settings correct (i.e., the sidetone is 
placed in the center -- or high spot -- of the filter), go through all 
the filters, one after the next, resetting each as noted below.  Use 
the index (numbered) settings rather than the frequency settings.  Move 
each number one or two numbers, say, lower, and then back to the 
original number.  Move to the next filter, do the same through all the 
filters.  Do this for both c and c-bar.  You may now (possibly) have 
the same tone when switching through the filters, at least if you are 
listening to a note that is at you chosen sidetone.

   If that works (and it does for me), great.  But a few weeks from now, 
you'll notice that one of the settings will be off by 10Hz again.  At 
this point, I just live with it.  If you don't worry about it, you'll 
find that it is really a non issue.

best wishes,

dave belsley, w1euy


On May 17, 2004, at 9:20 AM, Stan Rife wrote:

> Hello fellow Elecraft owners,
> 	I sent this query to Elecraft tech support, but I thought I would
> run it by you guys as well to see if anyone had any idea what, if 
> anything,
> may be going on. The text I sent Elecraft follows:
>
> 	K2 S/N 4216, assembly completed and operational. I notice that on at
> least one of the filter settings, when I switch from say FL1 to FL2 
> (in CW
> mode) I notice about a 10Hz change in the received CW (nor) signal. 
> When I
> switch to FL3 it then goes back to the originally received tone and 
> stays
> there through FL4 and back to FL1. CW Rev seems ok...I do not detect a 
> shift
> in tone on any of the FL settings there. I have listened on LSB and 
> USB (to
> a CW sig) and have detected the same thing on at least two FL 
> settings. Why
> would the received tone freq. be shifting? I do not see a change in VFO
> frequency, just the tone freq itself.
> 	I don't know if this is a problem or not, but when following the
> instructions for aligning the filters with Spectrogram, the center of 
> the
> filter is at different DAC values for each filter. Is this normal? For
> instance, if the center DAC value is 140 for FL1, then FL2 center DAC 
> count
> might be lower, somewhere around 130. It seems to get correspondingly 
> lower
> as I go to FL3 and FL4. In all cases, though, my CW nor and CW rev BFO
> frequencies are on the correct side of center...low side of center for 
> CW
> nor, and high side of center for CW rev. The filters appeared to line 
> up
> good and I was able to see the 600 Hz tone marker fall right in the 
> center
> of FL2-FL4. I set FL1 to where it best represented the pictures 
> provided in
> the literature, based on my interpretation of them.
> 	I have also adjusted FL1 to tailor my transmit audio somewhat...I
> have moved the LSB BFO frequency down 100 Hz and the USB BFO freq. up 
> 100
> Hz. I assumed that a shift in one direction for LSB must require an 
> equal
> shift for USB in the opposite direction to keep the audio the same for 
> both
> sidebands.
>
>
> Stan Rife
> WD5EWA
> Houston, TX
> K2 S/N 4216
>
>
>
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