[RTTY] Re: Noise with MMTTY

[Don Hill AA5AU]

This past weekend with the newly acquired '775 I noticed there seemed to be more
noise present with the 250 hz (455 IF) filter on that with it off (standard 500
hz).  Just the opposite happens in my TS-870's and I think it has a lot to do
with DSP in the IF of the Kenwoods.  However, after an hour or so in the
contest, I hooked up an NIR-12 to the audio output of the '775 and it made a
world of difference when with the narrow filter on even though the '775 is
suppose to have DSP in the audio.  I checked the DSP settings in the radio (you
can do all this stuff when operating only one radio and calling CQ! hi) and
really couldn't determine what was the best setting.

So DSP in the IF is probably a factor of all this as well.  However, the
receiver in the '775 is much "quieter" overall than that of the TS-870 and it
was a pleasure to use this "vintage" radio.

The best thing you can do, and this was mentioned by Jay WS7I, is to put a 250
hz filter in the 455 kHz IF.  Luckily I had an FL-53A in my old IC-751A that I
was able to put into the '775 just before the contest.

BTW, the '775/PW1 combo is a real killer.  Auto-switching a KW and having the
amp remember which antenna is used for which band was truly a wonderful
experience.  I still haven't decided whether I'll keep the rig or not.  I'm
thinking I might go with a '756PROII instead.  I did like the "dual watch"
feature of the '775 and was able to "tune the band" in between calling CQ.

73, Don AA5AU



-----Original Message-----
From: rtty-bounces at contesting.com [mailto:rtty-bounces at contesting.com] On Behalf
Of llindblom at juno.com
Sent: Tuesday, March 23, 2004 1:07 PM
To: wrt at dslextreme.com
Cc: RTTY at 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 at 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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