[Elecraft] How to check Your K2 filter alignment

[Don Brown]

Hi Gang

If you would like to check out your K2 filters here is a quick way to mak=
e sure you have it right. Set the band to 80 meters and set the VFO to 40=
00.00 select CW mode and FL1. You should hear the MPU 4.00 MHz clock as a=
 600 Hz tone assuming your side tone is set to 600. If not adjust the VFO=
 a little to zero beat with the spot tone. Now cycle through the filters =
FL1-FL4 and the frequency should not change at all or very little. Now wi=
thout touching the VFO frequency hold the CW REV button to select CW reve=
rse. Again the tone should not change with the reverse or when cycling th=
rough the filters.

Now switch to USB mode and change the VFO to 3999.40 and you should hear =
the same note. Cycle through the filters and it should not change. Change=
 to LSB and set the VFO to 4000.60 and you should hear the same 600 Hz no=
te when cycling. the filters. If it will do all of the above then you got=
 it set as good as it gets.

If your K2 is not performing up to snuff then get in there and set it up =
right. It sure makes the operation nice

Its  not that hard to get everything close to perfect if you will spend a=
 little time with WWV, Spectrogram and a noise generator.

The above method is the one I use to check out a k2 after I have done a c=
alibration

The first thing is to make sure the K2 is on frequency you can check that=
 by looking at WWV with Spectrogram looking for the 500 and 600 Hz tones =
on alternating minutes (you may need to wait a little they are not on all=
 minutes of the hour). Use USB or LSB mode. When you have the tones on th=
e spectrogram markers read the VFO frequency and write it down. Connect t=
he frequency probe to TP3 in FCNTR mode and adjust C22 on the control boa=
rd to change the indicated frequency by the amount needed to make the VFO=
 correct. Example the VFO is reading 20 counts high then change the frequ=
ency at TP3 20 counts lower. Move the counter probe to TP1 and select 40 =
meters and run CAL PLL. This should put your VFO on frequency.

Then use Spectrogram to set your filters. Preset them to the settings in =
the manual first so you are sure you are on the right side of the bandpas=
s then adjust the filters with Spectrogram to center the bandpass on a ma=
rker set at your sidetone frequency. A noise generator connected to the K=
2 antenna makes it easier to see the band pass. You may need to do all of=
 the above more than once to get everything right.

When setting up sideband move the bandpass so the lowest point on the ski=
rt on the left starts just a little past 0 Hz set each filter trying to d=
uplicate that left hand skirt.

Don Brown
KD5NDB


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