[Elecraft] K2 Filter Alignment

[Don Wilhelm]

Bernie,

Are you tuning the desired signal to your sidetone pitch - use the SPOT 
and match the signals to the same tone - when the two are quite close in 
pitch, you will hear a WOW WOW WOW sound of the beat frequency.  When 
that beat sound slows down to nothing, you are at Zero Beat.  Adjust the 
AF Gain control  (and the ST L menu if needed) to make the amplitude of 
the sidetone and the signal about the same to hear that beat note best.

If your tuning is not the problem, then give it another try with 
Spectrogram and a noise generator.
Make certain the CW DAC values (or frequencies if you are displaying 
that) are lower than the CWrev values.
Also make certain the menu sidetone pitch setting matches the center 
frequency you set for FL2, FL3 and FL4.  The transmit frequency is 
offset by that amount by the firmware.

For FL1, since it is wide, you cannot set its center at your sidetone 
pitch, but the passband must be entirely within the Spectrogram 
display.  Make sure you can see the left side of the passband skirt drop 
down significantly before reaching zero frequency.  Failure to do that 
will cause loss of the Single Signal reception - in other words, you 
will hear part of the opposite sideband.

There are also instructions on my website www.w3fpr.com.  Look at part 3 
of the article on K2 Dial Calibration.

BTW - multiply those widths by 10.  That is a 700 Hz filter, not 70 Hz.  
The last zero is not displayed.

73,
Don W3FPR

On 12/31/2012 12:42 PM, Bernie KF0QS wrote:
> Dear Folks:
>
> I am the proud owner of K2-10 #6922 and, so far, have been operating it
> exclusively on cw (I am building the SSB option right now, though I am a
> brass pounder).  It is a fine radio and has caused my TS-850S and AL-80 amp
> to gather a lot of dust.
>
> My only problem has been the filter alignment.  I have repeatedly tried to
> align the filters, and always seem to end up with a situation where the
> passband of the filters never falls within the passband of the receiver at
> its maximum bandwidth (I have it set for 150hz).  In other words, the
> received signal, when the receiver is right on it, always seems to fall
> outside of the 70hz filter (if I tune the receiver to copy the received
> signal with the 70hz filter in use, and then switch to the 40 and 20hz
> filters, the signal stays within the bandwith).
>
> The last time I tried to align the filters, I used a noise generator and
> Spectrogram, and followed Tom Hammond's (N0SS) instructions.  After doing
> this, I always need to turn on the RIT and turn a few hz below the received
> signal to bring it within the bandwith of the 70hz filter.
>
> What am I doing wrong?  For reference purposes, I have my sidetone set for
> 600hz.
>
>