[Elecraft] Strange KNB2 Behavior

[Mike Harris]

G'day,

Tried this out just on background noise (no antenna) and guess what,
toggling from Low Threshold to High Threshold toggles ON KDSP2 noise
reduction, hence the low audio out.

However, it isn't consistent.  I can cycle High-Low-High-Low sometimes
without NR coming on, at other times it happens every time.  One in the NR
mode it has never toggled out when switching Hi-Lo.

Also, this only happens in CW mode.  I haven't been able to make it happen
on USB or LSB.

FWIW.

Regards,

Mike VP8NO
(IOTA SA-002)
(GD18BH)

> Okay, this is a real strange one. After seeing the discussion
> about the KNB2 being affected by the KDSP2/KAT100
> combo, I decided to check out my blanker. Keep in mind
> that up until now the blanker has behaved perfectly.
> Here is the sequence:
>
>     High Threshold ----- normal audio out
>     Low  Threshold ----- normal audio out
>     High Threshold ----- very low audio out
>     Low  Threshold ----- very low audio out
>     High Threshold ----- normal audio out
>     Low  Threshold ----- normal audio out
>     High Threshold ----- very low audio out
>                                   .
>                                   .
>                                 etc
>                                   .
>                                   .
>
> Note that in the entire sequence the NB is not actually
> activated, only the threshold is being changed. Also
> this is entirely repeatable and not at all random. Clearly
> there seems to be some sort of toggle in the low/high
> transition that is affecting the audio output level.
>
> Any guesses? Could this be related to the other KNB2
> problem?
>
> I'll try to get around to measuring voltages on the board
> today?
>
> Doug
> W6JD
> K2 #1626