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
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