How can I extract TIME information from SDR Radio?

[Phishfry]

Lets say on ARM64 I want to avoid RTC module and GPS module but use an RTL-SDR stick for system time via ntpdate.

Is that doable? Bad idea?

 

[tingo]

How? Are you going to get the RTL-SDR stick to decode GPS signals?

 

[Phishfry]

That is what I as wondering. Is there a commandline demodulator for GPS like there is for ADS-B?

 

[Phishfry]

GNU Radio might be able to do this... I am researching that angle now.

 

[Phishfry]

GNSS-SDR

An open source Global Navigation Satellite Systems software-defined receiver.

gnss-sdr.org

Built on GNU-Radio we have something to try.

 

[Phishfry]

FreeBSD Instructions for locally building GNSS-SDR based on this:

Build and install GNSS-SDR

How to quickly build and install GNSS-SDR in your system.

gnss-sdr.org

pkg install fortran lapack armadillo
mkdir -p /gnss-sdr/build
cd /gnss-sdr
git clone https://github.com/gnss-sdr/gnss-sdr
cd /gnss-sdr/build
cmake ..
make
make install

 

[Phishfry]

Build Failed. Undefined symbols.

[ 93%] Linking CXX executable gnss-sdr
ld: error: undefined symbol: absl::lts_20250127::log_internal::LogMessage& absl::lts_20250127::log_internal::LogMessage::operator<<<int, 0>(int const&)
>>> referenced by control_thread.cc
>>>               control_thread.cc.o:(ControlThread::handle_signal(int)) in archive ../core/receiver/libcore_receiver.a
>>> referenced by file_configuration.cc
>>>               file_configuration.cc.o:(FileConfiguration::init()) in archive ../core/receiver/libcore_receiver.a
>>> referenced by gnss_flowgraph.cc
>>>               gnss_flowgraph.cc.o:(GNSSFlowgraph::set_channels_state()) in archive ../core/receiver/libcore_receiver.a
>>> referenced 101 more times

ld: error: undefined symbol: absl::lts_20250127::log_internal::LogMessage& absl::lts_20250127::log_internal::LogMessage::operator<<<unsigned int, 0>(unsigned int const&)
>>> referenced by gnss_flowgraph.cc
>>>               gnss_flowgraph.cc.o:(GNSSFlowgraph::connect_signal_sources_to_signal_conditioners()) in archive ../core/receiver/libcore_receiver.a
>>> referenced by gnss_flowgraph.cc
>>>               gnss_flowgraph.cc.o:(GNSSFlowgraph::connect_signal_sources_to_signal_conditioners()) in archive ../core/receiver/libcore_receiver.a
>>> referenced by gnss_flowgraph.cc
>>>               gnss_flowgraph.cc.o:(GNSSFlowgraph::connect_signal_sources_to_signal_conditioners()) in archive ../core/receiver/libcore_receiver.a
>>> referenced 235 more times

ld: error: undefined symbol: absl::lts_20250127::log_internal::LogMessage& absl::lts_20250127::log_internal::LogMessage::operator<<<unsigned long, 0>(unsigned long const&)
>>> referenced by gnss_flowgraph.cc
>>>               gnss_flowgraph.cc.o:(GNSSFlowgraph::connect_signal_conditioners_to_channels()) in archive ../core/receiver/libcore_receiver.a
>>> referenced by gnss_flowgraph.cc
>>>               gnss_flowgraph.cc.o:(GNSSFlowgraph::connect_signal_conditioners_to_channels()) in archive ../core/receiver/libcore_receiver.a
>>> referenced by gnss_flowgraph.cc
>>>               gnss_flowgraph.cc.o:(GNSSFlowgraph::check_signal_conditioners()) in archive ../core/receiver/libcore_receiver.a
>>> referenced 52 more times

ld: error: undefined symbol: absl::lts_20250127::log_internal::LogMessage& absl::lts_20250127::log_internal::LogMessage::operator<<<long, 0>(long const&)

 

[freezmi]

when conditions are just perfect I can pick up time signals from DCF77 on my radio clocks and my RSPdx. unfortunately it's outside the range of the rtl-sdr, but do search for 'dcf77' since there are cheap microcontroller-friendly rx/tx modules that can work at those almost-audio frequencies. and also various projects that use a soundcard plus a simple RX stage to receive the signal and digitize it.

have a look online if you have such a time code transmitter in your neighborhood.

an interesting link on sdr and dcf77 here

why avoid RTC tho? it guarantees time data when other time signals are unavailable.