48 lines
1.8 KiB
Plaintext
48 lines
1.8 KiB
Plaintext
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This file contains random notitions
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-----------------------------------
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Sample rates between 301000 Hz and 900000 Hz (inclusive) are not supported.
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They cause an invalid configuration of the RTL chip.
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rsamp_ratio = 28.8 MHz * 2**22 / sample_rate
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If bit 27 and bit 28 of rsamp_ratio are different, the RTL chip malfunctions.
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The RTL chip has a configurable 32-tap FIR filter.
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RTL-SDR currently configures it for cutoff at 1.2 MHz (2.4 MS/s).
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Casual test of ADC errors:
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* DC offset in order of 1 code step
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* I/Q gain mismatch in order of 4%
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* I/Q phase mismatch in order of 1% of sample interval
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With tuner in auto-gain mode, device autonomously switches between gain
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settings during a run. The tuner gain seems to switch between ~ 24 dB
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and ~ 34 dB without intermediate steps.
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With RTL in AGC mode, the level of the digital sample stream is normalized
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to -6 dBFS. Unknown whether this is an analog or digital gain stage.
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Unknown whether AGC mode is coupled to Elonics IF gain or purely
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a digital thing in the RTL chip.
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Does this improve SNR or not?
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Default settings in librtlsdr:
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Elonics LNA gain: when auto tuner gain: autonomous control with slow update
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otherwise gain as configured via rtlsdr_set_tuner_gain
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Elonics mixer gain: autonomous control disabled,
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gain depending on rtlsdr_set_tuner_gain
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Elonics IF linearity: optimize sensitivity (default), auto switch disabled
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Elonics IF gain: +6, +0, +0, +0, +9, +9 (non-standard mode)
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Elonics IF filters: matched to sample rate (note this may not be optimal)
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RTL AGC mode off
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Local radio stations:
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radio2 92600000 (good)
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radio3 96800000 (good)
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radio4 94300000 (bad)
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qmusic 100700000 (medium)
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radio538 102100000 (medium)
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radio10 103800000 (bad)
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radio west 89300000 (medium)
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