received from Juha Vierinen:
A student here noticed that there is dc bias even with the rafael tuner.
We looked into this issue and found that using 127.4f instead of 127.5f
removes this bias. I assume this is associated with a bug in the digital
downconversion of the RTL chip. This change fixes the problem.
The gnuradio block https://github.com/dl1ksv/gr-fcdproplus must be
installed before building gr-osmosdr.
Available named gains:
Dongle Classic:
LNA: -5 to 30 dB, in 2.5 dB steps
MIX: 4 or 12 dB
Dongle Pro+:
LNA: 0 or 1, meaning off/on only. no information about real values.
MIX: 0 or 1, meaning off/on only. no information about real values.
BB: 0 to 59 dB, in 1 dB steps
This patch also introduces optional "device" and "type" arguments which
allow to override the values automatically picked by gr-osmosdr:
osmocom_fft -a "fcd,device=hw:2,type=2"
The "device" argument overrides the audio device used by the underlying
driver to access the dongle's IQ sample stream.
The "type" argument selects the dongle type, 1 for Classic, 2 for Pro+.
Thanks to Alexey Bazhin for the initial patch and Volker Schroer for
testing.
features:
- gain control for AMP & VGA
- frequency error correction
- automatic baseband filter
- up to 20M sampling rate
limitations:
- no DC offset correction implemented (yet)
- high sampling rates may not work on slow machines
the following TX named gain stages are available:
RF: MGA-81563, switchable 0 or 14dB
IF: MAX2837 VGA, 0 to 47dB in 1dB steps
This allows a block to enable an associated driver to begin
transfering data just before we start to execute the scheduler.
The end result is that this reduces latency in the pipeline
when dealing with audio devices, usrps, etc.
the following named gain stages are available:
RF: MGA-81563, switchable 0 or 14dB
IF: MAX2837 LNA, 0 to 40dB in 8dB steps
BB: MAX2837 VGA, 0 to 62dB in 2dB steps
features:
- gain control for LNA & VGA
- frequency error correction
- automatic baseband filter
- up to 20M sampling rate
limitations:
- no DC offset correction implemented (yet)
- no RX preamplifier control (disabled by default)
- high sampling rates may not work on slow machines