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.
73 W0ETC
On Mon, 22 Mar 2004 14:16:44 -0600 "Charles Morrison"
<cfmorris@bellsouth.net> writes:
> This email originally started out as asking if anyone's seen noise on
> their
> MMTTY screens when its running, but I've since discovered something
> and want
> to ask a different question or opinion..
>
> I reinstalled MMTTY 2 weeks ago to try to get rid of the
> Userpara.blablalbabla error that pops up immediately following a
> reboot and
> starting Writelog. Well this didn't fix, so I quit worrying about
> it since
> I just exit and restart Writelog and then MMTTY will start without
> the
> error. More on that later.
>
> Anyway, while rushing I tried to recall everything that I had turned
> on or
> off and started clicking buttons. What I noticed worried me a bit
> and I've
> found the culprit but am wondering how much its affecting the
> decode.
>
> What I noticed was that regardless of what was plugged into the
> radio, what
> input settings on the mixer control was selected, what anything on
> the
> computer was set to, was that with absolutely NOTHING connected to
> the radio
> or the computer, MMTTY's XY scope still showed some sort of NOISE
> signal.
> Instead of it being a small dot in the middle, it looked as though I
> were
> receiving static or noise or something. If I cranked up the input,
> MIC or
> Line, it actually increased. Keep in mind that there's nothing but
> keyboard, mouse, power and monitor hooked to the computer.
>
> Well, I just got to playing around with it and it's the Band Pass
> Filter.
> Turn it off, the XY scope goes to a little dot, turn it on, and XY
> scope is
> active, with everything disconnected, irrelevant inputs selected
> (CDROM,
> Speaker) etc. Does this mean that there's additional noise in the
> decode
> loop? Is this going to affect my ability to decode weaker signals?
> Wouldn't it be better if when there's truly no signal present that
> the sound
> card is not detecting something? It would appear as though its
> hearing
> "something" when the band pass filter is turned on, because the XY
> scope is
> showing movement.
>
> What do yall think?
>
> Charlie
> KI5XP
>
>
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>
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