On 7/23/2024 11:57 AM, Andy Durbin K3WYC via wsjt-devel wrote:
I looked at the 180000 file using Audacity spectrum analysis. I did not
see the clear discrete frequencies that I was expecting but I have not
compared with a clean SF signal yet.
The artifacts may, as previously suggested, been due to a propagation
anomaly. However, I still suspect the artifacts were in the transmitted
signal.
The SuperFox waveform uses digital 129-FSK modulation with Gaussian
smoothing of transitions between tones, and modulation necessarily
involves sidebands. The "fuzz" that you see is not an artifact or a
defect. It's a necessary physical requirement. What you are seeing IS a
clean SF signal, only slightly modified by propagation effects.
The basic SuperFox modulation frequency or "symbol rate" is 12000/1024 =
11.719 Hz. Sidebands will be spaced from each other by this amount.
It's a mathematical fact that "clear discrete frequencies" of the sort
you're imagining cannot exist if the signal carries information and
therefore is modulated in some way.
-- 73, Joe, K1JT
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