Message-ID: <37C092E5.BEEB31DA@nephro.uni-kiel.de>
Date: Mon, 23 Aug 1999 02:16:37 +0200
From: "Peter W. Schnoor" <pwsch@nephro.uni-kiel.de>
Organization: University of Kiel, Clinic of Nephrology
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Comparison of FFTDSP4 and Specrogram 5.09 on QRS
References: <002401beecef$c01fc900$130a063e@default>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

Hello Group,
Hi Alan,

May be that it could be of interest to have an impression
how I'm working here 8-)

Alan Melia wrote:
 
> In conclusion, I still like FFTDSP4 as an operating aid. I find that on a
> full scan 200-2500Hz I can quickly locate a new station calling and
> concentrate the hardware on it. I have a paper template stuck to the bottom
> edge of the monior screen as there is no offset capability allowing the
> display to indicate the correct frequency (like there is on 'gram). I can
> see stations on hand keyed speeds that I cannot hear in the phones. I can
> see where the QRM is and shift the filter away to to listen to a weak
> station. Ok, a good CW operator could do this without the aid but it is nice
> to see what is happening ( and I am not a real morse operator!). I leave my
> RX tuned to 138.10 kHz LSB and use the pass-band tuning to 'isolate' the
> signal and BFO shift on the AOR 7030 to adjust to a listenable tone. 

I don't know FFTDSP4 and "'gram" since I'm running
SOLARIS/LINUX only. I have minor experiences (bad...) with
WINxx. I'm using SPECGRAM2 for UNIX systems on several INTEL
platforms. This application is available in source code (!)
and can be (re)compiled for X-Window and console (VGA/SVGA)
for your own. I'm running two modified versions, one for
overview, to watch the whole band, and the other for serious
VSCW purposes. There are many colour tables available which
can be switched in a turnaround manner (including "embossed"
modes). I can confirm your remarks on the worth of observing
the whole band for new signals. Behind my convertor there
are always two receivers running: One for this overview,
switched to USB / 2.4 kHz fixed and the other with approx.
100 Hz to locate an unknown signal for "hearing". So no
detectable signal will slip through your fingers. The
program never had been crashed even running for days.

> On the use of filters I have found that putting the required signal near the
> edge of my 500Hz IF filter, sometimes makes the tone of a weak signal stand
> out more from the sound of the
> filtered noise. Is this a normal technique known to morse men?

Yes! But normally this technique works well only if your
whole system behind the smallest filter will produce minor
noise (ears/hemisperes included...). Psychophysiological
studies have shown that some coloured noise may be helpful
in detecting weak signals especially in combination with
phase shifts between your ears ("Signal Detection in Noise",
Peter Montnemery, SM7CMY, MD thesis, Lund 1994, Sweden). May
be there are some kind of autocorrelation processes running
inside our brains. (Not always reliable here)

54°16'N / 10°04'E, JO54ag
73 es gl de Peter, DF3LP