[Elecraft] K2 Filter Alignment: more

[Don Brown]

Hi

MORE


As Ron explained the centering of the filters should only be done on the narrower filters below 1Khz. If you are setting up a wide CW filter or you are using the SSB filter as one of your CW filters (FL1) then you will set it up like the SSB filter with the lower slope starting to roll off at about 300 Hz and the upper slope rolling off at about what ever bandpass you are setting. I usually set the CW filters on a SSB equipped K2 to FL1=OP1 (2500 hz SSB filter), FL2=1000 hz, FL3=500 hz and FL4=200 hz. Setting the narrow filter much below 200 Hz will cause a fall of in receiver gain. If you need a narrower filter than this use the audio filter or DSP. It will get you down to about 80 Hz bandwidth without the loss of gain.

Don Brown


  ----- Original Message ----- 
  From: Don Brown<mailto:DolfinDon at msn.com> 
  To: elecraft at mailman.qth.net<mailto:elecraft at mailman.qth.net> ; Linden, Mike (BRC-Hes)<mailto:Mike.Linden at boschrexroth-us.com> 
  Sent: Tuesday, July 13, 2004 9:27 AM
  Subject: Re: [Elecraft] K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev


  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