My background both as a former professional musician and as a naval officer
with years of experience in hunting submarines by passive sonar (both
aurally and by waterfall display), what appears to be happening is that the
brain is quite able to effectively block out the "white noise" in its effort
to pull out intelligence. When you are listening to a faint CW signal the
brain actually hears all the extraneous signals as noise and "blanks" them
out. The intelligent signal is then heard. Apparently, in a silent
situation, the brain has to be "urged" to find the intelligence.
As far as an RTTY signal, I don't believe the sound detection circuit is
that smart, but I do believe that when one cranks the filters down too hard,
one actually loses part of the signal (outlying tones) and that makes it
more difficult to copy under noisy conditions.
My only problem is the tendency of my rig (TS-430) to clamp down the AGC
when a nearby loud signal comes on, thereby virtually eliminating the weaker
signal I may be copying. In that circumstance, a tight filter (or moving
the IF shift) will help.
Don
Don Inbody/AD0K
QSL via LotW and eQSL
-----Original Message-----
From: rtty-bounces@contesting.com [mailto:rtty-bounces@contesting.com] On
Behalf Of llindblom@juno.com
Sent: Tuesday, March 23, 2004 13:07
To: wrt@dslextreme.com
Cc: RTTY@CONTESTING.COM
Subject: Re: [RTTY] Re: Noise with MMTTY
As some one who over the past 40+ years has done a lot of all nighters on 80
and 160 during SSB contests, I learned I could copy signals better with the
widest filters in the rig. Eventually I started doing that on CW and it
worked well.
During BARTG I decide to try and take this one step further. For the weakest
of signals it seemed that going to the wide filters in my IC-775 did the
trick and let MMTTY decode cleaner. Or, did the signal peak when I went
wide and dive when I went back to a narrower setting?
73 W0ETC
-- Bill Turner <wrt@dslextreme.com> wrote:
On Tue, 23 Mar 2004 10:29:59 -0600, Charles Morrison wrote:
>I can't speak to this issue directly. However, on the human factors side
>people doing signal detection research stumbled across something that is
>counter intuitive. Is it easier to copy a weak CW signal on a quiet or
>noisy band?
>Many people will say it is easiest to copy CW on a quiet band. However,
>under controlled testing people did a better job of copying a weak CW
signal
>in noise than when there was no noise. A demonstration of this on NPR
>nearly blew me away. The played 10 seconds of what to the human ear
sounded
>like silence but actually contained a very low level CW signal. When noise
>was added in the CW signal was very obvious. Of course too much noise mask
>the signal entirely.
>I doubt electronic circuits/software work the same as the human brain.
But,
>the next time you operate the original digital mode don't cuss any noise
for
>it might be help your brain detect a signal that it otherwise might not
>process.
_________________________________________________________
I've noticed a similar effect on CW myself. Often I can copy CW better
with a wide filter instead of a narrow one, even though the apparent
noise is more. Strange.
--
Bill, W6WRT
QSLs via LoTW
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