WiNRADiO G69DDC User’s Guide
Filter Length
This facility makes it possible to adjust the digital filter “length” (which directly
translates into selectivity) for three types of filter used in the
Excalibur Sigma
:
The
Demodulator filter length
has a direct influence upon the
overall
'receiver selectivity'. Greater length produces better selectivity.
The maximum achievable selectivity is limited by the processing power of your
computer: The greater the CPU power, the “longer” (and therefore sharper) the
filter can be made.
This function also makes it possible to observe the
CPU load
, which will
depend upon this setting. It may not be advisable to select a value resulting in
more than say 30% CPU load, as the computer may then become sluggish.
The
Notch
and
Audio
filter lengths can also be adjusted using this facility,
resulting in sharper (or shallower) notch and audio filtering, tailored to specific
operator requirements.
Should the computer become sluggish or even “freeze” as a result of this
adjustment, please reduce the respective filter length to a lower value.
Note also that the CPU load can be lowered (while keeping selectivity high) by
reducing the DDC1 bandwidth. For example standard HF and narrow-band FM
signals can be demodulated with 20 kHz DDC1 bandwidth without a decrease
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