[Elecraft] K2 Noise Blanker Slot as Additional IF Amplifier Stage

[Don Wilhelm]

Dick,

Not an IF amplifier stage, but an added IF filter - check out
http://homepages.nildram.co.uk/%7Ebaker/K2_Overview.html to see if that
might address your stated needs.

If you have filter loss at bandwidths less than 1200 Hz, then I would
conclude that you have something wrong with your filter - the filter
typically does not show attenuation until the bandpass is reduced to less
than 200 Hz.  If you are certain your BFO frequencies are correct (the
filter peak is centered on your sidetone pitch), you should not experience
attenuation at reasonable filter widths - if you do, I would suspect that
you have a bad crystal in the filter.

73,
Don W3FPR


> -----Original Message-----

>
> Has anyone thought of, or tried modifying the K2 Noise Blanker to be an
> additional K2 IF amplifier stage?
>
> My problem is that when I really, really need the crystal filter, I am
> trying to copy a very weak (but readable) CW signal with adjacent
> S-9 QRM.
> When I switch in tighter than about 1200 Hz of crystal filtering,
> I tend to
> lose the target signal due to filter loss. ( Losing the target
> signal is not
> because the BFOs are not properly calibrated).
>
>   When I use just the DSP filter to block the adjacent S-9 QRM,
> then I still
> lose the target DX due to AGC "pumping" (without the IF "roofing"
> filter).
> I'd really like some additional IF gain to compensate for the
> crystal filter
> loss.
>
>   I would try using the Noise Blanker's U1, MC1350, as the added
> IF stage,
> and use U3, the Controller's decoded program lines to adjust U1's
> AGC input
> for front panel gain control.  I could use P1's pin 8, 8R, as
> power for the
> MC1350 so that it's only active on "receive".
>
>