[Elecraft] Ripple in K2 xtal filter?

[Stephen Prior]

I didn't build my K2 (I wish had!), so I have limited experience of its
alignment.

Having finally got around to getting back on psk31, I have noticed a banding
effect in the waterfall - both with mixw on the pc and cocoamodem on the
mac.  Removing the audio feed from the K2 shows the usual digital artifacts
often observed with integrated soundcards in particular, but no evidence of
any ripple.  I'm using the inbuilt sound on a new Intel mac mini running
both Leopard and XP.  I don't believe the computer is to blame. Anyway, as
noted below, the OP1 filter shows none of this.

Running spectrogram with random noise at the antenna (not much else on 12m,
four hours after dark!), I can see a distinct ripple in the passband of all
filter widths, in every mode.  Except, that the OP1 filter in the ssb board
gives a flat response in all modes. So it's something to do I guess with the
setup of the variable crystal filter. I am wondering how far back I will
need to go in the setting up of the K2 to find the adjustment which will
perhaps flatten the shape.

Using spectrogram (latest) with the xtal filter in usb at 2.1kHz, there is
about 10dB between peak and trough of the ripple.  The peaks are roughly
600Hz apart.  I'd never noticed this in casual listening, I doubt that I
could have done.  Most of the time I am on cw and the 700Hz filter setting
shows no obvious ripple anyway.  It does however certainly not look right on
the waterfall on psk31!

I'd be grateful for any advice!

Thanks,

Stephen G4SJP