[Elecraft] K3 - LO CUT/HI CUT bugs

[Joe Planisky]

Up until recently, I had only used the SHIFT/WIDTH functions for  
setting the DSP filter parameters.  This morning I decided to try the  
LO CUT/HI CUT functions.  I really don't understand the behavior I'm  
seeing and I suspect there's something wrong.

I'm using FW 2.67 and DSP 1.96. I have the FM filter in FL1, and the  
2.7KHz filter in FL2.  No other filters currently installed.  Both the  
FM and 2.7K filters are enabled for SSB and CW Rx.

I'll start with SSB mode.

I expected the LO and HI values to be independently adjustable with  
the only limitation that the HI value must be higher than the LO  
value.  However, I find that for HI values greater than 2.70, the  
maximum LO value I can dial in is lower, Hz for Hz.  In other words,  
the LO and HI limits track in opposite directions when the HI value is  
 > 2.70.  Example:

HI value    Max LO value
2.70        2.50
2.80        2.40
2.90        2.30
3.00        2.20
3.10        2.10
...         ...
4.10        1.10

With the HI value 2.70 or lower, the maximum LO value is always 0.20  
less than the HI value, which seems reasonable.

Trying to use LO/HI CUT mode in CW mode reveals the same sort of  
behavior described above except the HI value where the controls start  
the divergent tracking is 1.05.

There are a lot of other odd behaviors in CW mode that simply don't  
make any sense.

E.g. the LO and HI values can be set to the same value (e.g. 1.00 and  
1.00).  I suspect the actual bandwidth in this case is 50 Hz.  Not a  
biggie but I would expect the closest separation in the displayed  
values to be 50 Hz (0.95 and 1.00).

E.g. if I start in SHIFT/WIDTH mode with BW=2.80 and FC=1.10 and then  
switch to LO/HI mode, the maximum HI value I can set is 2.50.  If I  
start with BW=2.8 and FC=0.60 then switch, the maximum HI value I can  
set is 2.00.  Various other BW and FC settings result in other maximum  
HI values.

E.g. if I start with BW=2.8/FC=0.60 then switch, the MINIMUM HI value  
I can set is 1.00, UNTIL I activate the LO control (e.g. by turning it  
counterclockwise, which doesn't actually change the current value of  
0.00), then I can set HI values lower than 1.00.

E.g. Depending on the exact BW/FC values I start with, when I switch,  
sometimes the LO and HI values are at a 50 Hz boundary.  That is, 2.15  
instead of 2.10, and the step size seems to always be 100 Hz (2.15 ->  
2.05 -> 1.95 etc.)

These oddities aren't apparent in normal day-to-day operation, but I  
think they're pretty clearly unintended.

73
--
Joe KB8AP