N8ME:
>Maybe I'm wrong, but can I assume that the narrower filters have a greater
minimum length? If so, my observations have a strange quirk. I don't
remember the exact numbers, but as I was reducing the bandwith from say,
1000 Hz, at 280 Hz, the filtering went wide open. However, when I continued
down to 270 Hz, the filtering was restored. Then at 200 no filtering, 190
filtering, etc.
If you are doing this test with low Tap
settings, you may want to look at the response
with a spectrum analysis program before concluding
there is a real problem. With a low number of taps,
the DSP filter may become like a comb response
with multiple peaks off the primary response. These
can fool your ears depending on what the spectrum
response is. It may sound like filtering is "wide
open" to your ears, when in fact it is not. This
applies both to single 10 Hz BW changes and to
single Tap setting changes. One small change can
sound very dramatic to your ears.
It's interesting to experiment with Tap
settings for very weak signals. I sometimes
prefer less than the maximum 199 for weak
signals and narrow bandwidths. For example,
154 and 99 sometimes seem better under certain
noise conditions. I don't believe there's any
substitute for simply experimenting to find what
produces the best S/N for your ears under the
specific noise conditions. There is no magic
"set and forget" setting that works for all
conditions.
73, Bill W4ZV
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