I should add that you should drive the K2 audio sufficiently, then adjust the power knob for the desired power output. Attempting to use the audio level to adjust the power output will result in "Power Hunting" and could be the cause of some of your problems. The proper audio level for the K2 can be determined by watching the ALC indication on the LED bargraph.  Set the DISPLAY to indicate ALC, then --- Increase the audio until you have the rightmost bar flashing, and then reduce the audio until it just goes out.

The K2 gain may be different for each band due to changing gain in the RF Chain with frequency.  So you may have to adjust the audio level for each band.

If you are using SSB mode, make certain that SSBC is set to 1-1 to assure no compression.  You can turn the RTTY filter set on and align that filter set.  The SSBC setting is independent of that used for SSB so you can leave your SSB compression setting in place.

73,
Don W3FPR
-------------------------------------------------------------------------------------------------------------------------------
How old is this K2? Those K2s with Serial Numbers below 2560 have the original IF crystals. You will achieve a flatter passband if the crystals on the KSB2 board (and the RF Board) are replaced with the upgrades crystals.

If your KSB2 card is older, check the resistors on that board against the newer schematic to be certain the PSK mod has been added to that option board.

Make certain the filter alignment is done correctly and that the OP1 filter is selected for the FL1 filter.

Do a complete filter alignment using a visual aid like an audio spectrum analyzer like Spectrogram running on your computer and a broadband noise source (like the Elecraft N-Gen) connected to the K2 antenna. You can find Spectrogram on my website www.w3fpr.com - scroll down on the home page to near the end.

Don't overlook the possibility that your soundcard may not be producing a flat response.

73,
Don W3FPR

On 12/3/2019 3:22 AM, Markku Siipola wrote:
I have started to use my K2 for FT8, with the KIO2 digital interface and the SSB-module. My sound card is connected to the hear phone and microfon connections. Software WSJT-X, JTAlert and DXLab commander.

On 80m and 40m all is ok, but not on the higher bands. For example on 20 m, the power is reduce very much for certain LF frequences. I tested this by using the TUNE function in WSJT-X and changing the TX frequence.

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