[Elecraft] K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

[Don Brown]

Hi

Actually this is fairly easy to do with spectrogram. First use the new method listed on the Elecraft website to make sure C22 is set right. I use the 600 and 500 Hz tones on 10 Mhz WWV to get the tuning right on a 600 and 500 Hz marker in spectrogram. Then go back and forth between TP2 and TP3 to get Khz and Hz to match (ignore the Mhz). Then run Cal PLL. Once the VFO is calibrated I connect the noise generator and set each of the CW filters centered on 600 HZ (or whatever your side tone is). You need to move every one of the filters even if it is good so the firmware will recalculate the offset. The SSB filters should be set so the fall off slope starts at about 300 Hz and drops to the baseline by about 100 hz. Try to get the LSB and USB to look as close to the same as possible. The frequency readings should be close to the range listed in the BFO setting table in the manual. If the frequency is way off you have set the filter on the wrong side of the slope. Move it back in the ball park listed in the table and then center the band pass in spectrogram. As a final test remove the antenna and tune to 4.000 MHz and check the tone of the 4 MHz clock on each CW and CW reverse filter. The tone should not change frequency. Set the VFO to 4.00060 Mhz and check for the same tone on LSB then set the VFO to 3.99940 Mhz and check USB. In all cases you should hear the same 600 hz tone If not then you need to redo one or more of the filters.


Don Brown


  ----- Original Message ----- 
  From: Linden, Mike (BRC-Hes)<mailto:Mike.Linden at boschrexroth-us.com> 
  To: elecraft at mailman.qth.net<mailto:elecraft at mailman.qth.net> 
  Sent: Tuesday, July 13, 2004 8:16 AM
  Subject: [Elecraft] K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev


    Once I get to the Stage III alignment on my K2, I plan on using
  Spectrogram to align the CW and SSB filters/BFOs. It seems that proper
  filter alignment is a juggling act between the following:

  1) Proper centering of the signal within the filter's passband: For the most
  part, CW should be aligned in the center or the largest peak, SSB should be
  aligned for best audio quality (usually with the bottom at about 300Hz).

  2) Constant pitch across the different bandwidth filters for a given mode.
  In other words, you should hear very little pitch change (<= 20Hz or so) as
  you move from the widest filter for a given mode to the narrowest filter for
  that same mode.

  3) Constant pitch as you switch between USB/LSB on an accurately tuned AM
  signal like WWV and constant pitch as you switch between CW and CW-Reverse
  on an accurately tuned CW signal.

    Is it difficult to satisfy number 3 if you tune the filters with
  Spectrogram based on number 1? Has anyone come up with a reliable
  methodology for doing this, or is it just something that you pretty much
  play with until you are satisfied?

    Thanks, Michael N9BDF
            K2 #4137


  PS  The "Amateur Radio Emergency Communications Consistency Act" (HR 1478)
  and the "Amateur Radio Spectrum Protection Act" (HR 713 & S. 537) are in
  Congress. Please contact your Congressmen to ask for their support of these
  bills! See the following ARRL link for details:
  http://www.arrl.org/govrelations/<http://www.arrl.org/govrelations/> <http://www.arrl.org/govrelations/<http://www.arrl.org/govrelations/>> 


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