My 2 cents:
For "rag chewing" the stock "wide" filter is fine.
In fact, I still use the stock SSB filter in both of my K3s and I am a
pretty serious contester (nobody holds more current CQWW USA contest
records than I do).
Remember that a roofing filter is NOT what determines your "final IF
bandwidth." It does, apparently, contribute "a little," but the DSP
filtering is mostly what is doing that.
So for me, the difference between how many signals are going to fall
inside your passband when from 2.7 to 2.1 to 1.8 on SSB is, well, not
much. If anyone in the USA has such a concern, for me, is
appropriate only for contesting. Even when DXing, either your calling
on "his" frequency or if split, well, hopefully he is asked for a
split of more than just "up 1." Remember, this is SSB. Some will say
that on 80/160, there are a very few number of DXing occasions where
the narrower SSB filter can help. I won't argue that.
I have to wonder out loud how many guys are "feeling" the DSP filter
width impact when they go from their 2.7 to 2.1 to 1.8 on SSB versus
how much of that is improvement in IMD reduction specs. For 99%, they
probably are "feeling" the narrower DSP filter impact (which means the
narrower roofing filter has essentially no impact at all). If the SSB
band is packed with wall-to-wall very, very, very strong signals, then
I'm betting that the roofing filter BW just won't matter for the vast
majority of ops.
Are there times when the narrower roofing filters are better?
Probably a handful per contest. But for me, when contesting, I really
don't want to deal with such a situation. I can probably have a
better rate (if I'm running) by finding a better QRG to attempt to run
(call CQ). It's mostly how much you want to "defend your frequency"
versus how much you want to improve your QSO rate. YMMV.
So to summarize...for my 2 cents, for "rag-chewing" the stock SSB filter is VFB.
de Doug KR2Q
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