[ARC5] S+N/N ratio results - wet filter

[Dennis Monticelli]

Bill,

I agree with everything you said.  Our brain+ear combo represent a
sophisticated analog signal processor.  It does much more than discern
frequency.  It also discerns phase, amplitude and will "sync" to a
distinctive signal.  Unlike a conventional DSP it has the ability to learn
and store the signature of a signal.  Try the following test:  Tune into a
CW signal among QRM with the bandwidth wide at first.  Don't sit there for
very long, but note the difficulty of copy.  Then switch in a narrow
bandwidth and copy the signal for a couple of minutes.  Then switch the
filter back to wide.  You will still be able to copy the signal as well as
you did with the narrow filter.  Your brain has been trained to hone in on
that particular signal.  It always amazes me when I do this simple test.

Having said all that, I agree that a modern narrow linear-phase filter can
very useful for weak signal work.   I depend upon a top-notch DSP for
raising the S/N when working CW DX.

Whenever I put the T-22 on the air, it's "character" never fails to draw
attention.....usually the good kind :-)

Dennis AE6C


On Fri, Jun 14, 2013 at 5:17 AM, Bill Cromwell <wrcromwell at gmail.com> wrote:

> Hi,
>
> Some unmentioned details about the wet filters from "the good old days". I
> have told other hams on other lists that the "grey filter" on the air works
> the same way it does in a popular, crowded restaurant. We listen to one
> voice and one conversation while totally immersed in dozens of  other,
> nearby voices. By the way...there is a limit to how much of that we can do
> and it varies day to day and even hour to hour. The extreme example...we're
> unlikely to notice a gnat belch in a hurricane. The term 'rotten QRM' is
> not something new.
>
> It's especially easy to sort out the one voice in the crowd when it's our
> sweetheart doing the talking (grin). So the grey filter uses all of the
> "data" available to do it's job. Today most of the transmitters are pretty
> much sterile and so is the CW being sent by microprocessors. In the good
> old days a lot (most? (all?)) of the transmitters had what can be called
> "character". Add to the transmitters' character the different 'voices' of
> the fists keying them. One that stands out in my mind was WB8MTD in the
> 80's on QMN. One dit and we knew it was him. There was no chirp and no
> identifiable hum on his signal but his transmitter's voice was dramatically
> *different*. It was a much easier proposition to even learn how to sort the
> signals by ear than it is to apply the already 'trained' grey filter now.
> Lucky for us there aren't as many signals on the air these days - except
> contest weekends - for whatever reason.
>
> Using narrow filters, especially if there is any trace of ringing, is
> fatiguing. I run filtering to help lift very weak signals out of the noise
> and for that they are invaluable. Most of the time during the week I just
> use the SSB or AM filters even on CW. It's more pleasant. I can hear what's
> happening on a small chunk of the band while I'm working on other things. I
> like Ken's "grey spectrum analyzer" concept.
>
> 73,
>
> Bill  KU8H
>
> ______________________________**______________________________**__
> ARC5 mailing list
> Home: http://mailman.qth.net/**mailman/listinfo/arc5<http://mailman.qth.net/mailman/listinfo/arc5>
> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>