DA0LF Received by G3XDV 21 June 1998
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| DA0LF carried out a new set of tests from a better location than
when I first heard him. Using the new Spectrogram v4.2, I received a very
solid screen trace from his 20s dot period extremely slow Morse. I could
occasionally detect him by ear but extremely weakly. At the time I was also
hearing LX1PD and G2AJV in my 500Hz receiver passband - three countries
at once!! |
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A dash - 60 seconds long. fading can be seen about 10s from
the start. This is absolutely 100 per cent copy despite the signal
being inaudible. Note how the static crashes (see the yellow line) are ignored
by the averaging - compare with the wide bandwidth plot below. |
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The two dots of the 'F' in DA0LF |
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The slow CW test ran from 0800 to 1000. After about 0900 the
signal improved to allow occasional copy by ear. This trace shows a 60-second
dash from DA0LF as a continuous line about half-way up the screen. As can
be seen from the readable signal from G2AJV's 5WPM, the DSP bandwidth is
very much broader than in the screens above. It clearly shows that conventional
speed CW could have been just about readable - note that at this bandwidth
the screen is about as good as a practiced CW operator. Comparison between
this screen and the top two screens shows just how much improvement in signal/noise
ratio is possible by using extremely slow Morse. |
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| Click here to download a .WAV audio file
of DA0LF at 0930UTC (beware - the 2-minute recording takes
up1.3 Megabytes). Use it to experiment with Spectrogram if you have just
downloaded a copy (or any other DSP program), or to see how DA0LF was received
here - or just to hear how amazing it is to get such good copy on screen
from such an incredibly weak signal. It is just possible to hear
Peter's signal by ear if you really concentrate hard. The audio tone is
612Hz, which is a few hundred Hertz above G2AJV's beacon which can be heard
throughout. Some facts you may need when playing with Spectrogram: About
18 seconds in (later if you use the averaging facility in Spectrogram 4.2),
a dash starts, lasts for 60 seconds, then there is a 20s gap followed by
a dot 20s long. |
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