James Moritz wrote:
> Dear Andy & Group,
> With a 1Hz Bandwidth, isn't it rather difficult to find the
signals
> in the first place? How do you tell if what you are receiving is a
> signal or not? It seems to me that some radically different
> operating procedures will have to be devised to exploit extreme
> narrow band techniques such as these!
>
It has to be assumed you know the operating frequency beforehand to the
required accuracy - being able to adjust to within 1 Hz should be
trivial at these frequencies where it is even difficult to pull a
crystal that far off frequency.
You will know a signal is there when the demodulator or display responds
in the correct manner.
Alberto Wrote:
Spectran presently applies a Hamming window to the incoming data.
If you think it would be useful to use a rectangular one, perhaps
selectable with a push-button, it is an easy change to the program
I don't think a rectangular window will offer much extra value in a
crowded band like 137kHz ( ! ) the sidelobes of other signals could
cause visual QRM offsetting the 1.8 times bandwidth advantage. I've
played with many window types and come to the conclusion that the
Hamming or Hanning windows are the best compromise every time. By the
look of Spectrogram, it also uses one of these.
Andy G4JNT
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