KDSP2 low pass and bypass problems

[Vincent Denecker]

My KDSP2 seems to operate normally except for two problems.
 
1/ LOW PASS
CW (widest bandwidth, 800Hz)
No problems when increasing the center frequency up to 1.1 kHz -
Spectogram confirms the filter setting.
However, setting the center frequency to 1.2 kHz seems to actually lower
the center frequency down to 1.0 kHz.
Increasing further the center frequency set point results in LPASS being
dispayed, but now the filter setting seems to be exactly the same as
with 1.1 kHz center / 0.8 kHz bandwith. The pass band is not as broad as
expected, the lower frequency is a few hundreds rather than a few tens
of Hertz.
 
RTTY (widest bandwidth, 2 kHz)
Same problem as for CW.
No problems when increasing the center frequency up to 2.3 kHz.
However, setting the center frequency to 2.4 kHz seems to actually lower
the center frequency down to 2.2 kHz.
Increasing further the center frequency results in LPASS being dispayed,
but now the filter setting seems to be exactly the same as with 2.3 kHz
center / 2.0 kHz bandwidth.
 
SSB
Looks ok.
 
2/ BYPASS MODE
The bypass mode can be set to DSP BYP using the menu.
However, this does not actually bypass the KDSP2. In CW and RTTY, it
looks like a change to a 2.3 kHz center / 2.0 kHz bandwidth filter (same
as observed in RTTY LPASS mode). In SSB, it looks like a sharp filter
with a 1000 Hz low cut and a 2000 Hz high cut.
 
Any solution to this problem? Thanks in advance.
 
Vincent, G0LMX
K2 #5326
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[KK7P]

> 2/ BYPASS MODE
> The bypass mode can be set to DSP BYP using the menu.
> However, this does not actually bypass the KDSP2.

Please note the current the K2 is drawing (use the DISP button) when in
operating mode and in bypass mode.  If the current drain is reduced, the
KDSP2 is bypassed and the effect is from something else, perhaps the
current crystal filter setting.

In bypass mode, the DSP goes into a low power mode and the CODEC is
mostly turned off, just leaving the analog section operating to pass the
signal through.

73,

Lyle KK7P

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