The TS-870 lacks a cw filter ahead of the DSP. Kenwood attempts to
compensate by passband shifting of the two SSB filters to narrow the
bandwidth, but that doesn't result in a great CW filter. As a result,
dynamic range for nearby signals is limited to by the A/D converter to
around 60 dB. No amount of fancy DSP after the A/D converter can
improve this. By comparison, a pair of cascaded 500 Hz crystal
filters should provide over 100 dB of dynamic range at 1 kHz
separation. Until someone figures out how to build a fast 24 bit A/D
converter, all DSP receivers without narrow crystal filters will have
this limitation.
--
73,
Scott K9MA
sdelling@facstaff.wisc.edu
--
CQ-Contest on WWW: http://www.contesting.com/_cq-contest/
Administrative requests: cq-contest-REQUEST@contesting.com
|