[Elecraft] Re: roofing filters - when to use them

[Ken N9VV]

Hi Doug, I wanted to relate to your assessment of "narrow" filters. 
When I was first introduced to Ham Radio I was very fortunate to 
meet Harry W9TT. Harry was a super-duper NTS operator and net 
control. He *INSISTED* that I keep his old BC-??? set to the WIDEST 
setting for his CW nets. The obvious reason was that in 1960 many of 
the 80M crystals we ground ourselves were in the "ball park" but not 
dead zero beat on the NCS. If he sent two guys down 2 or 3k to pass 
traffic, he wanted to hear them in the peripheral vision in his 
head. That way he "knew" when they were through passing their 
traffic and he would anticipate their return or sending someone else 
down to meet them. He taught me to simply listen to one station of 
interest and let the others carry on. I have never understood the 
obsession of the modern CW ops with *narrow* filters. I use my brain 
and don't seem to miss any QSOs ;-)
TU for reading,
72/73 de Ken N9VV (K9DNY 1960)

DOUGLAS ZWIEBEL wrote:
> Hi all:
> 
> Well, Bill (ZV) gave a nice (brief) summary and pointed to a nice
> reference.  Ten Tec had (maybe it is still there) some good info also,
> but specific to their radio...however, you can still use it to get a
> "feel" for a what a roofing is (and what it isn't).  If you're a
> member of ARRL, go to their web page and search on Roofing Filter.
> 
> Don (FPR) cited some uses which I am not familiar with (data), so no
> comment from me on that.
> 
> I've commented directly to the source about my "wonder" at why one
> would want a variable roofing filter.  As Lee said, one "wide" and one
> "narrow" is enough (at least for SSB / CW only operation).
> 
> If I'm  on CW and my radio is hearing squeaks, pops, and "garbage" due
> to lots of LOUD signals being in my passband (say 15 or 20kc wide on
> an "old" radio), I would not be able to do much...maybe cut back on
> the RF gain, add some attenuation, etc.  However, if I could narrow
> the passband (the roof) to say 1kc, the likelihood of two (or more)
> very loud signals being captured within that 1kc is greatly reduced.
> If I use a 500hz roofing filter (assuming all other parameters could
> remain unchanged), the odds of having two (or more) "other" very
> strong signals there (besides the one I want to copy) is even
> less...hence less chance of squeaks and pops masking the signal I want
> to copy.  BTW, the squeaks and pops = IMD Products.
> 
> Of course, if there were that many LOUD signals that close together,
> I'd simply move (qsy) to a clearer (relatively) spot.
> 
> Why in the world one would want to take the time to "carefully" or
> "slowly" adjust a roofing filter's bandwidth is beyond me.  I would
> simply dump in my "narrow" roofing filter and be done with it.  Either
> it works or it doesn't; why play around?
> 
> This topic is of major concern to contesters, especially (mostly) on
> the low bands.  I know...it is also of concern to Europeans on 40m
> even NOT during a contest...true.
> 
> If you're not a SERIOUS contester or Low Band DXer (or data guy ala
> Don's description?), I have a hard time understanding why you'd want
> these "narrow" filters.  Hey look, 2.7kc is pretty darn narrow
> compared to most of what is out there.  Again (as had already been
> cited), even the IC7800 and FT9000 have a 3kc roofing filter as their
> narrowest (which I don't think is good enough for some CW situation).
> 
> I would guess that for 95% of non-serious contesters, or non-low band
> DXer (and digital guys?), you'll be VERY happy with a single 2.7kc
> roofing filter for SSB and even for CW.  For those who are used to IF
> filters, this is just not the same.  You'll still have that with the
> K3....twiddle the bandwidth any way you like (narrow).  Remember,
> roofing filters are for CROWDED band condx FILLED with LOUD signals
> (with the digital proviso still there).
> 
> And NOW, I'd like to say, I have no idea exactly how much MAGIC the
> Aptos boyz have included in this radio and for all I know (not having
> the radio, the specs, schematic, code, etc., they may have come up
> with something that voids all of the above.  Wouldn't that be great!
> 
> de Doug KR2Q
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