Hi Huub,
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I worked a bit more on the calibration today, and had a bit more success.? You can see the result in the attached image.? It is a bit closer to linearity than yours, but still a bit flat on the lower end.? Here is what I ended up with:
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SDRconsole:?
HF attenuation: 0
HF Gain: 20
Visual Gain: -30
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SDRc2RSS:
FFT Window: None
dB Threshold: -145
Gain: 2.2
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There is an interesting article on the web:
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which discusses the noise floors in different environments.? The Dark Sky Observatory is best described as "quiet rural".? In that case the noise floor may be -130 dB or lower.? In more noisy environments it can be quite a bit higher.? The dB Threshold on SDRc2RSS corresponds to that noise floor, and one should not raise it above the actual noise floor else some faint signals will be lost.? That article suggests that in low noise environments, RX-888 Mk II might benefit from a small amount of RF pre-amplification before the SDR.? Larry Dodd also suggested the same.
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I am not completely satisfied with this calibration.? These settings result in a very dark background on the RSS output, in some places black.? This may be partially a function of our radio-quiet background at the Dark Sky Observatory.? I think trying out a small amount of pre-amplification is a good idea, and I have ordered an RF pre-amp and will give it a try when it comes.
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Richard
