Hi group,
is there more you can do with that CW carrier-component than simply detect
the presence of a signal without being able to decode it? Well, we could use
it to guide a large adaptive array to regain the data rate:
- 100 receivers in different locations across Europe record audio files of a
highly desired DX-station transmitting 3 s qrss, buried -10 dB in the noise,
- offline, we extract the frequency offset and phase of the DX carrier
components in each file using low bandwidth (e.g. 3 mHz). We also estimate
their signal-to-noise ratios;
- using this information as a phase reference, we convert each file to
baseband (like in a synchronous AM-detector),
- then add up the baseband data from all files, weighted by their SNR. Using
the carriers as pilots, we effectively have focused our large sparse array on
a small area around the transmitter, gaining some 20 dB in signal to noise
ratio,
- and we finally extract the information at full data rate in its original
0.3 Hz bandwidth, saving a factor of 100 in time and transmitted energy.
Just a thought after a glass of wine, or maybe good for something?
73s de Markus, DF6NM
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