[Elecraft] KX3 - range of filter centre frequency in DATA-A mode too limited

[Darren Long]

Hi,

I wonder why the range of centre frequency in DATA-A mode is so narrow.  I've
recently started dabbling with FSQCall and have some issues optimising the KX3's
filter for reception in this mode.  FSQCall's waterfall shows the received audio
spectrum between roughly 50Hz and 1630Hz, it's modem has a waveform bandwidth of
300Hz with a nominal centre frequency of about 1150Hz.

I'd like to set my rx filter passband with a centre of about 1150Hz and a
bandwidth of about 500Hz, but this can't be easily achieved.  The best I can do
is to set the filter fc at 1.28kHz, the bandwidth to 0.65kHz and block some more
at the top end of the desired passband by activating the notch filter (which is
quite broad) set to 1520Hz.

Is there any good reason that the range of usable filter centre frequencies in
DATA-A mode is limited from 1.28 to 1.72kHz?  A larger range would be much more
useful.

Cheers, 73

Darren, G0HWW