I have been playing with a SDR-1k recently. The
filter scheme in that radio allows down to a 10hz
bandwidth. What I have discovered is there is no
ringing in a filter this narrow generated by the
algorithm used in the SDR, even if the signal being
received has a bandwidth considerably wider than 10
hz. (up to 200hz for example). Precise tuning of the
received signal is a requirement.
It doesn't make as much difference regarding noise and
S/N. There is a clear difference to the ear between
100hz and say 25hz in terms of "noise" in the
background, but there is not much change in
copy-ability of a bloody weak signal. What does make
a huge difference is on the copy-ability of signals
that are very close to each other. In the recent DX
contest I was able to work S3 signals that were within
50hz to 100hz of S9+20 signals. If I opened the
bandwidth to 100hz the QSO would not have been
possible. I could still hear some clix from the nearby
strong station as would be expected, but the clix were
in the same s-3 range as the weak station and as such
copy could be easily achieved.
The NR algorithm in the SDR doesn't do much. That
particular algorithm is better in the Orion though
personally I don't find NR in either rig to be of much
use.
73 W9OY
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