osmocom-sdr

osmocom-sdr@lists.osmocom.org

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906 discussions

[PATCH] call libsub_intertrupt_event_handler in rtlsdr_cancel_async
by Jasper 26 Jan '22

26 Jan '22

Please find below a patch as per suggestion of Martin Ling: call libusb_interrupt_event_handler in rtlsdr_cancel_async to trigger the event loop handler to look at the async_cancel variable. (https://lists.osmocom.org/hyperkitty/list/osmocom-sdr@lists.osmocom.org/thr…) I have tested timings on a windows 11 machine with and without the patch when running a async transfer at two different sampling rates: sample rate with without theory 1536K 0 - 2 ms 0 - 84 ms 85 ms 288K 0 - 4 ms 0 - 457 ms 455 ms The table shows the range of timings to cancel the async transfer as measured over a couple of runs. The "theory" column shows the theoretical time to complete one transfer at the particular sampling rate (i.e. driven by the size of a transfer buffer). And indeed, on some machines it appears that cancelling the async transfer, if unlucky, can take as much time as waiting for a full transfer to complete. The call to libsub_intertrupt_event_handler fixes that. For large transfer buffers and/or low sample rates this can make a difference. Thanks to Martin for sharing the insight. Jasper Author: jvde.github <jvde.github(a)gmail.com> Date: Wed Jan 26 19:00:55 2022 +0100 call interrupt_event_handler in cancel_async diff --git a/src/librtlsdr.c b/src/librtlsdr.c index 67e30c4..b949692 100644 --- a/src/librtlsdr.c +++ b/src/librtlsdr.c @@ -1948,6 +1948,9 @@ int rtlsdr_cancel_async(rtlsdr_dev_t *dev) if (RTLSDR_RUNNING == dev->async_status) { dev->async_status = RTLSDR_CANCELING; dev->async_cancel = 1; + + libusb_interrupt_event_handler(dev->ctx); + return 0; }

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[PATCH] count number of open transfers and ensure zero open transfers before freeing memory
by Jasper 24 Jan '22

24 Jan '22

Hi all, As per discussion with Martin Ling on this mailing list, please find below a proposed patch that simplifies the async_read, keeps track of open tranfers and checks for zero open transfers before closing to avoid unidentified behaviour at close. Thanks, Jasper commit 4b06ae321e91296f13355a0715e9a961b4f57e45 Author: jvde.github <jvde.github(a)gmail.com> Date: Mon Jan 24 20:15:34 2022 +0100 count live transfers before close diff --git a/src/librtlsdr.c b/src/librtlsdr.c index 096abae..67e30c4 100644 --- a/src/librtlsdr.c +++ b/src/librtlsdr.c @@ -119,6 +119,7 @@ struct rtlsdr_dev { int dev_lost; int driver_active; unsigned int xfer_errors; + int live_transfers; }; void rtlsdr_set_gpio_bit(rtlsdr_dev_t *dev, uint8_t gpio, int val); @@ -1695,11 +1696,15 @@ static void LIBUSB_CALL _libusb_callback(struct libusb_transfer *xfer) { rtlsdr_dev_t *dev = (rtlsdr_dev_t *)xfer->user_data; + dev->live_transfers --; + if (LIBUSB_TRANSFER_COMPLETED == xfer->status) { if (dev->cb) dev->cb(xfer->buffer, xfer->actual_length, dev->cb_ctx); - libusb_submit_transfer(xfer); /* resubmit transfer */ + if(!dev->async_cancel) + if( libusb_submit_transfer(xfer) == 0) /* resubmit transfer */ + dev->live_transfers++; dev->xfer_errors = 0; } else if (LIBUSB_TRANSFER_CANCELLED != xfer->status) { #ifndef _WIN32 @@ -1847,9 +1852,9 @@ int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx, { unsigned int i; int r = 0; + int ret = 0; struct timeval tv = { 1, 0 }; - struct timeval zerotv = { 0, 0 }; - enum rtlsdr_async_status next_status = RTLSDR_INACTIVE; + struct timeval canceltv = { 0, 50 }; if (!dev) return -1; @@ -1863,6 +1868,7 @@ int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx, dev->cb = cb; dev->cb_ctx = ctx; + if (buf_num > 0) dev->xfer_buf_num = buf_num; else @@ -1875,6 +1881,8 @@ int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx, _rtlsdr_alloc_async_buffers(dev); + dev->live_transfers = 0; + for(i = 0; i < dev->xfer_buf_num; ++i) { libusb_fill_bulk_transfer(dev->xfer[i], dev->devh, @@ -1894,64 +1902,41 @@ int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx, "echo 0 > /sys/module/usbcore" "/parameters/usbfs_memory_mb\n", i); dev->async_status = RTLSDR_CANCELING; + ret = -3; break; } + else + dev->live_transfers++; } - while (RTLSDR_INACTIVE != dev->async_status) { + while (RTLSDR_RUNNING == dev->async_status) { r = libusb_handle_events_timeout_completed(dev->ctx, &tv, - &dev->async_cancel); + &dev->async_cancel); if (r < 0) { /*fprintf(stderr, "handle_events returned: %d\n", r);*/ if (r == LIBUSB_ERROR_INTERRUPTED) /* stray signal */ continue; - break; + rtlsdr_cancel_async(dev); + ret = -4; } + } - if (RTLSDR_CANCELING == dev->async_status) { - next_status = RTLSDR_INACTIVE; + if (!dev->xfer) return -5; - if (!dev->xfer) - break; + for(i = 0; i < dev->xfer_buf_num; ++i) + if (dev->xfer[i]) + libusb_cancel_transfer(dev->xfer[i]); - for(i = 0; i < dev->xfer_buf_num; ++i) { - if (!dev->xfer[i]) - continue; + for (i = 0; i < dev->xfer_buf_num && dev->live_transfers > 0; ++i) + libusb_handle_events_timeout_completed(dev->ctx, &canceltv, NULL); - if (LIBUSB_TRANSFER_CANCELLED != - dev->xfer[i]->status) { - r = libusb_cancel_transfer(dev->xfer[i]); - /* handle events after canceling - * to allow transfer status to - * propagate */ -#ifdef _WIN32 - Sleep(1); -#endif - libusb_handle_events_timeout_completed(dev->ctx, - &zerotv, NULL); - if (r < 0) - continue; - - next_status = RTLSDR_CANCELING; - } - } - - if (dev->dev_lost || RTLSDR_INACTIVE == next_status) { - /* handle any events that still need to - * be handled before exiting after we - * just cancelled all transfers */ - libusb_handle_events_timeout_completed(dev->ctx, - &zerotv, NULL); - break; - } - } - } + if(dev->live_transfers > 0) return -6; _rtlsdr_free_async_buffers(dev); - dev->async_status = next_status; + dev->async_status = RTLSDR_INACTIVE; - return r; + return ret; } int rtlsdr_cancel_async(rtlsdr_dev_t *dev)

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[PATCH] librtlsdr: force wait state after lib_cancel_transfer to avoid crash on close in windows
by Jasper van den Eshof 24 Jan '22

24 Jan '22

Good day! I was struggling with an occasional crash of the rtl-sdr tools on windows when closing the device after pressing CTRL-C. Both with the versions as provided with VCPKG and when directly compiling the latest version in MSVC (with latest of libusb). It is a bit difficult to spot a crash at close as usually it is silent but you can see it running it from MSVC or in a debugger. It does not happen always but frequent enough. Also, consider this example for the binary versions from Jan 2 (https://ftp.osmocom.org/binaries/windows/rtl-sdr/): C:\>rtl_adsb.exe Found 1 device(s): 0: Realtek, RTL2838UHIDIR, SN: 00000001 Using device 0: Generic RTL2832U OEM Found Rafael Micro R820T tuner .... Signal caught, exiting! User cancel, exiting... C:\>echo %ERRORLEVEL% -1073741819 After investigation of the libusb logs and experimentation I think this crash can be avoided by 1) defining zerotv in rtlsdr_read_async as 1 ms instead of zero (see libusb/libusb#1043) or 2) include a short call to Sleep to allow async operations to finish. Please find below a patch for the latter fix for your consideration. More information, here: https://github.com/osmocom/rtl-sdr/pull/18 and here: https://github.com/libusb/libusb/issues/1043 Thanks for your great work on the rtlsdr library and kind regards. Author: jvde.github <jvde.github(a)gmail.com> Date: Sat Jan 8 13:30:34 2022 +0100 force wait state after cancel of usb transfer and before handling usb events diff --git a/src/librtlsdr.c b/src/librtlsdr.c index 0146298..2682d77 100644 --- a/src/librtlsdr.c +++ b/src/librtlsdr.c @@ -1930,6 +1930,9 @@ int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx, /* handle events after canceling * to allow transfer status to * propagate */ +#ifdef _WIN32 + Sleep(1); +#endif libusb_handle_events_timeout_completed(dev->ctx, &zerotv, NULL); if (r < 0)

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[PATCH] fix build issue on macOS by adding libusb shared lib directory to search path
by Jasper 24 Jan '22

24 Jan '22

Hi all, on some systems building librtlsdr can fail when libusb-1.0 is not installed in the standard library locations (e.g. macOS with libusb installed via homebrew can have the shared library in /usr/local/Cellar/libusb/1.0.24/lib). The below patch includes LIBUSB_LIBRARY_DIRS in the search path for the linker to correct this issue. For your kind consideration. Thanks, Jasper Author: jvde.github <jvde.github(a)gmail.com> Date: Mon Jan 24 19:21:44 2022 +0100 fix build for macOS diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt index 7b47309..3b8060b 100644 --- a/src/CMakeLists.txt +++ b/src/CMakeLists.txt @@ -21,6 +21,7 @@ add_library(rtlsdr SHARED librtlsdr.c tuner_e4k.c tuner_fc0012.c tuner_fc0013.c tuner_fc2580.c tuner_r82xx.c) target_link_libraries(rtlsdr ${LIBUSB_LIBRARIES} ${THREADS_PTHREADS_LIBRARY}) +target_link_directories(rtlsdr PUBLIC ${LIBUSB_LIBRARY_DIRS}) target_include_directories(rtlsdr PUBLIC $<BUILD_INTERFACE:${CMAKE_SOURCE_DIR}/include> $<INSTALL_INTERFACE:include> # <prefix>/include

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[PATCH] rfspace: Add PPM correction
by argilo＠gmail.com 23 Jan '22

23 Jan '22

From: Clayton Smith <argilo(a)gmail.com> This patch was originally written by Alexandru Csete and posted at https://github.com/csete/gr-osmosdr-gqrx/commit/d66df300. The only change I made was to rename the _freq_corr_ppm variable to _freq_corr, since many other devices use that name. This patch used to be included in Gqrx releases, so it should work correctly. --- lib/rfspace/rfspace_source_c.cc | 17 +++++++++++++---- lib/rfspace/rfspace_source_c.h | 2 ++ 2 files changed, 15 insertions(+), 4 deletions(-) diff --git a/lib/rfspace/rfspace_source_c.cc b/lib/rfspace/rfspace_source_c.cc index 314dfc732d..113588a5d4 100644 --- a/lib/rfspace/rfspace_source_c.cc +++ b/lib/rfspace/rfspace_source_c.cc @@ -103,6 +103,7 @@ rfspace_source_c::rfspace_source_c (const std::string &args) _nchan(1), _sample_rate(NAN), _bandwidth(0.0f), + _freq_corr(0.0), _fifo(NULL) { std::string host = ""; @@ -446,6 +447,8 @@ rfspace_source_c::rfspace_source_c (const std::string &args) _thread = gr::thread::thread( boost::bind(&rfspace_source_c::tcp_keepalive_task, this) ); } + _center_freq = get_center_freq(); + #if 0 std::cerr << "sample_rates: " << get_sample_rates().to_pp_string() << std::endl; std::cerr << "sample rate: " << (uint32_t)get_sample_rate() << std::endl; @@ -600,7 +603,7 @@ static size_t read_bytes( int fd, char *data, size_t size, bool &run ) int nread = read( fd, &data[nbytes], 1 ); if ( nread == 0 ) - continue; + continue; if ( nread < 0 ) break; @@ -1378,7 +1381,10 @@ osmosdr::freq_range_t rfspace_source_c::get_freq_range( size_t chan ) double rfspace_source_c::set_center_freq( double freq, size_t chan ) { - uint32_t u32_freq = freq; + uint32_t u32_freq; + + u32_freq = freq * (1.0 + _freq_corr * 0.000001); + _center_freq = freq; /* SDR-IQ 5.2.2 Receiver Frequency */ /* SDR-IP 4.2.2 Receiver Frequency */ @@ -1395,7 +1401,7 @@ double rfspace_source_c::set_center_freq( double freq, size_t chan ) transaction( tune, sizeof(tune) ); - return get_center_freq( chan ); + return _center_freq; } double rfspace_source_c::get_center_freq( size_t chan ) @@ -1423,12 +1429,15 @@ double rfspace_source_c::get_center_freq( size_t chan ) double rfspace_source_c::set_freq_corr( double ppm, size_t chan ) { + _freq_corr = ppm; + set_center_freq( _center_freq, chan ); + return get_freq_corr( chan ); } double rfspace_source_c::get_freq_corr( size_t chan ) { - return 0; + return _freq_corr; } std::vector<std::string> rfspace_source_c::get_gain_names( size_t chan ) diff --git a/lib/rfspace/rfspace_source_c.h b/lib/rfspace/rfspace_source_c.h index 996f47b392..42bb6de6ac 100644 --- a/lib/rfspace/rfspace_source_c.h +++ b/lib/rfspace/rfspace_source_c.h @@ -145,6 +145,8 @@ private: /* members */ size_t _nchan; double _sample_rate; double _bandwidth; + double _center_freq; + double _freq_corr; gr::thread::thread _thread; bool _run_usb_read_task; -- 2.25.1

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[PATCH] Stop applying workaround for libusb < 1.0.9
by argilo＠gmail.com 19 Jan '22

19 Jan '22

From: Clayton Smith <argilo(a)gmail.com> Librtlsdr has a workaround for libusb versions that lack libusb_handle_events_timeout_completed, which was added in version 1.0.9 (released 2012-04-02). The workaround is always applied unless the HAVE_LIBUSB_HANDLE_EVENTS_TIMEOUT_COMPLETED macro is set, but the cmake code that sets this macro was removed in 849f8efca42b659bf7e8fe17156ee0aa67b47233. As a result, the workaround is now always applied. This results in an extra 1-second delay whenever a GNU Radio flowgraph containing an RTL-SDR block is stopped, which makes operations like switching between demodulators in Gqrx annoyingly slow. To solve this problem, I've simply removed the workaround, as it should no longer be needed. I wonder if perhaps the workaround recently applied in 2659e2df31e592d74d6dd264a4f5ce242c6369c8 might stem from the same bug. --- src/librtlsdr.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/src/librtlsdr.c b/src/librtlsdr.c index 2682d77ec2..096abaeffc 100644 --- a/src/librtlsdr.c +++ b/src/librtlsdr.c @@ -39,12 +39,6 @@ #define LIBUSB_CALL #endif -/* libusb < 1.0.9 doesn't have libusb_handle_events_timeout_completed */ -#ifndef HAVE_LIBUSB_HANDLE_EVENTS_TIMEOUT_COMPLETED -#define libusb_handle_events_timeout_completed(ctx, tv, c) \ - libusb_handle_events_timeout(ctx, tv) -#endif - /* two raised to the power of n */ #define TWO_POW(n) ((double)(1ULL<<(n))) -- 2.25.1

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[PATCH] Show readable error when hackrf start/stop fails
by Martin Ling 04 Jan '22

04 Jan '22

Error codes from libhackrf are not very legible, and in the case of HACKRF_ERROR_LIBUSB, don't uniquely describe the cause of the error. Calling hackrf_error_name() provides a human-readable message, and in the case of libusb errors, identifies the actual cause rather than just indicating that the error came from libusb. This came up whilst trying to diagnose a libhackrf bug which showed up when using libhackrf, via gr-osmosdr, via gqrx: https://github.com/greatscottgadgets/hackrf/issues/883 --- lib/hackrf/hackrf_source_c.cc | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/lib/hackrf/hackrf_source_c.cc b/lib/hackrf/hackrf_source_c.cc index 03ea3bd..2826924 100644 --- a/lib/hackrf/hackrf_source_c.cc +++ b/lib/hackrf/hackrf_source_c.cc @@ -170,7 +170,8 @@ bool hackrf_source_c::start() hackrf_common::start(); int ret = hackrf_start_rx( _dev.get(), _hackrf_rx_callback, (void *)this ); if ( ret != HACKRF_SUCCESS ) { - std::cerr << "Failed to start RX streaming (" << ret << ")" << std::endl; + const char *msg = hackrf_error_name( (enum hackrf_error) ret ); + std::cerr << "Failed to start RX streaming (" << ret << ": " << msg << ")" << std::endl; return false; } return true; @@ -184,7 +185,8 @@ bool hackrf_source_c::stop() hackrf_common::stop(); int ret = hackrf_stop_rx( _dev.get() ); if ( ret != HACKRF_SUCCESS ) { - std::cerr << "Failed to stop RX streaming (" << ret << ")" << std::endl; + const char *msg = hackrf_error_name( (enum hackrf_error) ret ); + std::cerr << "Failed to stop RX streaming (" << ret << ": " << msg << ")" << std::endl; return false; } return true; -- 2.30.2

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lists.osmocom.org migrated to mailman3
by Harald Welte 03 Jan '22

03 Jan '22

Dear Osmocom community, today our mailing list server lists.osmocom.org has finally been migrated from mailman2-on-freebsd to mailman3-on-linux. This also included a variety of changes to DNS. I'll spare you the details, but everything _should_ be up and running now. * The List-Id headers should not have changed. * all list subscriptions + user accounts have been converted. * old 'static html' archives are still available (read only) at URLs like https://lists.osmocom.org/pipermail/baseband-devel/ * old List URLs like https://lists.osmocom.org/mailman/listinfo/baseband-devel are redirected to their respective modern counterparts In case you notice any mailing list related problem, please don't hesitate to contact me. Happy hacking, Harald -- - Harald Welte <laforge(a)osmocom.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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None
by None 03 Jan '22

03 Jan '22

o decode the VOR's morse code station ID. From that, I will have a shor= t list of VORs that I can currently receive. From those, if the geometry is= appropriate (I know the VORs positions from a database) I can calculate a = position.<u></u><u></u></p> </div><div><p class=3D"MsoNormal"><u></u> <u></u></p></div><div><p cla= ss=3D"MsoNormal">The software then just round-robin tunes the VORs in range= and continually tries to calculate positions. If too many drop out, it ret= urns to the initial scan mode.<u></u><u></u></p> </div><div><p class=3D"MsoNormal"><u></u> <u></u></p></div><div><p cla= ss=3D"MsoNormal">Not being able to receive this VOR or that VOR is not gene= rally a problem, but obviously, the more the better. With extra VORs I have= better options for choosing the closest ones or the ones with the best geo= metry.<u></u><u></u></p> </div><div><p class=3D"MsoNormal"><u></u> <u></u></p></div><div><p cla= ss=3D"MsoNormal"><u></u> <u></u></p></div><div><p class=3D"MsoNormal">= This is actually quite difficult to test, because VORs can generally only b= e received line-of-sight -- which means in the air. I'm a private pilot= but I found that flying and noodling with a laptop is too much trouble. Fr= om my office window, on a high floor in Oakland, CA, I can receive one VOR = from the Oakland airport. And I have now discovered a ridge near my home wi= th a scenic overlook from which I can receive two.<u></u><u></u></p> </div><div><p class=3D"MsoNormal"><u></u> <u></u></p></div><div><p cla= ss=3D"MsoNormal">I've tested the software enough to know that the initi= al scan function seems to work, and the morse decoding kind of works, but I= am not confident I'll get it to work very well. (One transmitter's= dit looks a lot like another's dah.) The nav signal decoding is simple= . (A 30 Hz AM modulated tone is phase compared with a 30 Hz tone FM modulat= ed at 9960 Hz. The phase obtained is the azimuth to the station.)<u></u><u>= </u></p> </div><div><p class=3D"MsoNormal"><u></u> <u></u></p></div><div><p cla= ss=3D"MsoNormal"><u></u> <u></u></p></div><div><p class=3D"MsoNormal">= If I ever get this working, I looking forward to sharing it with the commun= ity. In the process of building this, I created a simple SDR toolkit of DSP= functions. It's like Gnuradio in concept, but 16b fixed-point, and has= no external dependencies, and C89, so is easier to build on weird and limi= ted platforms. It also has perl bindings. Compared to GR, it looks like the= work of a rank amateur just learning DSP, but I do like the concept of the= re being a GR-like library out there, lightweight and embedded-friendly.<u>= </u><u></u></p> </div><div><p class=3D"MsoNormal"><u></u> <u></u></p></div><div><p cla= ss=3D"MsoNormal"><u></u> <u></u></p></div><div><p class=3D"MsoNormal">= Regards,<u></u><u></u></p></div><div><p class=3D"MsoNormal">Dave J<u></u><u= ></u></p></div> <div><div><div><p class=3D"MsoNormal" style=3D"margin-bottom:12.0pt"><u></u= > <u></u></p><div><p class=3D"MsoNormal">On Tue, Oct 22, 2013 at 3:06 = AM, jdow <<a href=3D"mailto:jdow@earthlink.net" target=3D"_blank">jdow@e= arthlink.net</a>> wrote:<u></u><u></u></p> <p class=3D"MsoNormal">He sent me two frequencies in private email. These w= ere in the FM<br>broadcast band (in the US). He probably needs to notch the= m out<br>in order to get adequate response.<br><br>As for wanting narrow ba= ndwidth - I am not quite sure why he thinks<br> that is a benefit. I use a large FFT (about 10 Hz per bin) and use<br>the z= oom control to see fine detail. (Different FFT settings suite<br>different = uses. This one seems to be a good compromise with my two<br>needs. I'm = too lazy to change it.)<br> <br>{^_^}<u></u><u></u></p><div><div><p class=3D"MsoNormal"><br><br><br>On = 2013/10/22 02:08, Sylvain Munaut wrote:<u></u><u></u></p><blockquote style= =3D"border:none;border-left:solid #cccccc 1.0pt;padding:0cm 0cm 0cm 6.0pt;m= argin-left:4.8pt;margin-right:0cm"> <p class=3D"MsoNormal">Effective filtering must occur between antenna and r= eceiver. All the<br>problems that a saturated preamp and ADC cause can&rsqu= o;t be repaired by<br>software. Never.<u></u><u></u></p></blockquote><p cla= ss=3D"MsoNormal" style=3D"margin-bottom:12.0pt"> <br>But his original problem is not with saturated preamps or ADC ... it&#3= 9;s<br>aliasing ... and that can be solved in the digital domain provided<b= r>fast enough ADC.<br><br>Cheers,<br><br>    Sylvain<br><br><u></= u><u></u></p> </div></div></div><p class=3D"MsoNormal"><u></u> <u></u></p></div></di= v></div></div></div><p class=3D"MsoNormal"><u></u> <u></u></p></div></= div></div></div></div></div></blockquote></div><br></div> --001a11346d7c0fd5fd04f20c4ef9--

1 0

None
by None 03 Jan '22

03 Jan '22

receive. From those, if the geometry is appropriate (I know the VORs = positions from a database) I can calculate a = position.<o:p></o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal>The software then just round-robin tunes the VORs in = range and continually tries to calculate positions. If too many drop = out, it returns to the initial scan mode.<o:p></o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal>Not being able to receive this VOR or that VOR is not = generally a problem, but obviously, the more the better. With extra VORs = I have better options for choosing the closest ones or the ones with the = best geometry.<o:p></o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal>This is actually quite difficult to test, because VORs = can generally only be received line-of-sight -- which means in the air. = I'm a private pilot but I found that flying and noodling with a laptop = is too much trouble. From my office window, on a high floor in Oakland, = CA, I can receive one VOR from the Oakland airport. And I have now = discovered a ridge near my home with a scenic overlook from which I can = receive two.<o:p></o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal>I've tested the software enough to know that the = initial scan function seems to work, and the morse decoding kind of = works, but I am not confident I'll get it to work very well. (One = transmitter's dit looks a lot like another's dah.) The nav signal = decoding is simple. (A 30 Hz AM modulated tone is phase compared with a = 30 Hz tone FM modulated at 9960 Hz. The phase obtained is the azimuth to = the station.)<o:p></o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal>If I ever get this working, I looking forward to = sharing it with the community. In the process of building this, I = created a simple SDR toolkit of DSP functions. It's like Gnuradio in = concept, but 16b fixed-point, and has no external dependencies, and C89, = so is easier to build on weird and limited platforms. It also has perl = bindings. Compared to GR, it looks like the work of a rank amateur just = learning DSP, but I do like the concept of there being a GR-like library = out there, lightweight and = embedded-friendly.<o:p></o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal><o:p> </o:p></p></div><div><p = class=3DMsoNormal>Regards,<o:p></o:p></p></div><div><p = class=3DMsoNormal>Dave J<o:p></o:p></p></div><div><div><div><p = class=3DMsoNormal = style=3D'margin-bottom:12.0pt'><o:p> </o:p></p><div><p = class=3DMsoNormal>On Tue, Oct 22, 2013 at 3:06 AM, jdow <<a = href=3D"mailto:jdow@earthlink.net" = target=3D"_blank">jdow(a)earthlink.net</a>> wrote:<o:p></o:p></p><p = class=3DMsoNormal>He sent me two frequencies in private email. These = were in the FM<br>broadcast band (in the US). He probably needs to notch = them out<br>in order to get adequate response.<br><br>As for wanting = narrow bandwidth - I am not quite sure why he thinks<br>that is a = benefit. I use a large FFT (about 10 Hz per bin) and use<br>the zoom = control to see fine detail. (Different FFT settings suite<br>different = uses. This one seems to be a good compromise with my two<br>needs. I'm = too lazy to change it.)<br><br>{^_^}<o:p></o:p></p><div><div><p = class=3DMsoNormal><br><br><br>On 2013/10/22 02:08, Sylvain Munaut = wrote:<o:p></o:p></p><blockquote style=3D'border:none;border-left:solid = #CCCCCC 1.0pt;padding:0cm 0cm 0cm = 6.0pt;margin-left:4.8pt;margin-right:0cm'><p class=3DMsoNormal>Effective = filtering must occur between antenna and receiver. All the<br>problems = that a saturated preamp and ADC cause can’t be repaired = by<br>software. Never.<o:p></o:p></p></blockquote><p class=3DMsoNormal = style=3D'margin-bottom:12.0pt'><br>But his original problem is not with = saturated preamps or ADC ... it's<br>aliasing ... and that can be solved = in the digital domain provided<br>fast enough = ADC.<br><br>Cheers,<br><br>    = Sylvain<br><br><o:p></o:p></p></div></div></div><p = class=3DMsoNormal><o:p> </o:p></p></div></div></div></div></div><p = class=3DMsoNormal><o:p> </o:p></p></div></div></div></body></html> ------=_NextPart_000_0073_01CF2656.CE93A820--

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