This topic has been pretty thoroughly discussed, so excuse my
additional comments. In summary, I think the majority feel either
the 2.7 or 2.8 KHz filter adequate for "general use", since one has
the ability to narrow bw using DSP.
I have only the 2.8 (in both Rx) and 400-Hz filter (in the main Rx).
I do mainly weak-signal work where narrow bw is important to reduce
"white noise". On CW-eme it is common to run at 100Hz for this
purpose as it increases SNR. The DSP filter handles that really well
since the objective is to eliminate noise at the detector (which the
DSP filter does).
A narrow roofing filter has significant use keeping strong off-freq
RF from causing IMD, or affecting the RF gain stages. This is
typically found in high-density HF contests (which I do not participate in).
I chose the 8-pole filters thinking the steeper skirts might offer a
slight advantage in crowded band conditions. For HF CW the 400-Hz
filter makes copy really "arm-chair nice" as it "almost" results in
hearing only the one intended station in the passband. On CW-eme I
haven't decided if 400-Hz roofing filter offers any advantage over
the DSP filter. I suspect not.
That all being said, I did order the roofing filter for my new
KX3. Why? Because I expect to travel with it to areas where that
will be more important. Hill-toping with it portable can expose one
to nearby strong signals (even IF feed-thru when running with VHF-mw
transverters). Being a direct-conversion SDR, RF filtering is more
important to keep out unwanted RF energy. So roofing filters
generally will not hurt performance if used and may help in some situations.
73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
DUBUS Magazine USA Rep
[hidden email]
Coming Soon - "Kits made by KL7UW"
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