Hi everyone,
although there are some comparisons between the R820T and the E4000
already [1, 2], I also did some tests with another use-case in mind.
I'm working on a thing similar to RTLSDR-Scanner [3]. I want to
monitor a large part of the spectrum continuously.
So I compared the R820T with the E4000 using RTLSDR-Scanner w/ and w/o
an antenna.
My results are here:
https://docs.google.com/folder/d/0ByDAKwyEiyx_XzZ5ZnpRV1VZWDQ/edit?usp=shar…
There's much more spurs with the E4000 than w/ the R820T. According to
[1, 2] one also would expect a better overall sensivity compared to
the E4000.
However, the GSM900 signals for example seem to be way better with the
E4000 according to the RTLSDR-Scanner. Tuning to a certain channel w/
OsmoSDR Source in GNUradio gives about the same SNR - contrary to the
RTLSDR-Scanner output. Can anyone explain this?
Also, the DVB-T channel at 502MHz is quite weak in the R820T
RTLSDR-Scanner output when compared to the E4000. I had a closer look
at the lower limit of the channel in gnuradio. This can be seen in the
502MHz_*.png pictures. The E4000 produces a nice +20dB step while one
can hardly see the channel in the R820T spectrum. I don't understand
this as well. Is this AGC-related? Manually setting a fixed gain
didn't really help though...
Any explanations?
Thank you!
Best regards,
Hunz
[1] http://steve-m.de/projects/rtl-sdr/tuner_comparison/
[2] http://www.hamradioscience.com/rtl2832u-r820t-vs-rtl2832u-e4000/#more-1852
[3] https://github.com/EarToEarOak/RTLSDR-Scanner
This is with a version of rtl-sdr I got by git last night and OpenBSD 5.2 (current release). 5.2 has some pthreads fixing so I waited until I bought another computer and loaded it. Are the crashes related to threads? I don't know, but possibly. It didn't work with OpenBSD 5.0 either.
rtl_fm crashes and uses threads
rtl_adsb crashes and uses threads
rtl_tcp doesn't crash, uses threads, actually stops on ctrl-c
rtl_test doesn't crash, doesn't use threads, won't stop
rtl_eeprom doesn't crash, doesn't use threads, ends normally
I'm not real practiced using gdb but I tried looking at a couple of core files, here's a run of rtl_fm:
rtl_fm -f 162550000 -N - | play -t raw -r 24k -e signed-integer -b 16 -c 1
-V1 -
-: (raw)
Encoding: Signed PCM
Channels: 1 @ 16-bit
Samplerate: 24000Hz
Replaygain: off
Duration: unknown
In:0.00% 00:00:00.00 [00:00:00.00] Out:0 [ | ] Clip:0
Found 1 device(s):
0: Realtek, RTL2838UHIDIR, SN: 00000013
Using device 0: ezcap USB 2.0 DVB-T/DAB/FM dongle
Found Rafael Micro R820T tuner
Oversampling input by: 42x.
Oversampling output by: 1x.
Buffer size: 8.13ms
Tuned to 162802000 Hz.
Sampling at 1008000 Hz.
Output at 24000 Hz.
Exact sample rate is: 1008000.009613 Hz
Tuner gain set to automatic.
In:0.00% 00:00:00.00 [00:00:00.00] Out:0 [ | ] Clip:0
Done.
Abort (core dumped)
d530# gdb -c rtl_fm.core /usr/local/bin/rtl_fm
GNU gdb 6.3
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "i386-unknown-openbsd5.2"...
Core was generated by `rtl_fm'.
Program terminated with signal 6, Aborted.
Reading symbols from /usr/lib/libpthread.so.16.0...done.
Loaded symbols for /usr/lib/libpthread.so.16.0
Reading symbols from /usr/lib/libm.so.7.0...done.
Loaded symbols for /usr/lib/libm.so.7.0
Reading symbols from /usr/local/lib/librtlsdr.so.0.0...done.
Loaded symbols for /usr/local/lib/librtlsdr.so.0.0
Reading symbols from /usr/local/lib/libusb-1.0.so.1.0...done.
Loaded symbols for /usr/local/lib/libusb-1.0.so.1.0
Symbols already loaded for /usr/lib/libpthread.so.16.0
Reading symbols from /usr/lib/libc.so.65.0...done.
Loaded symbols for /usr/lib/libc.so.65.0
Loaded symbols for /usr/libexec/ld.so
#0 0x0abbd98d in kill () from /usr/lib/libc.so.65.0
(gdb) bt
#0 0x0abbd98d in kill () from /usr/lib/libc.so.65.0
#1 0x0ac29545 in abort () at /usr/src/lib/libc/stdlib/abort.c:68
#2 0x005e9298 in pthread_mutex_unlock (mutexp=0x3c003d8c)
at /usr/src/lib/librthread/rthread_sync.c:218
#3 0x1c00266e in full_demod (fm=0xcfa2de5c)
at /usr/src/misc/osmocom/2013-04-15/rtl-sdr/src/rtl_fm.c:583
#4 0x1c0028ff in demod_thread_fn (arg=0xcfa2de5c)
at /usr/src/misc/osmocom/2013-04-15/rtl-sdr/src/rtl_fm.c:641
#5 0x005ebc2e in _rthread_start (v=0x84da4c00)
at /usr/src/lib/librthread/rthread.c:111
#6 0x0aba62e9 in __tfork_thread () from /usr/lib/libc.so.65.0
The backtrace (bt) shows that it dies trying to do a mutex_unlock (I think). rtl_tcp also does a mutex_unlock and it doesn't crash. I'm probably reading it wrong for all I know. I don't know what's causing the signal 6 either.
I'd also like to get the -lrt of of the cmake files. OpenBSD doesn't use or have lrt, it works without. I can edit it out and compile, but every time I run cmake again, I have to edit the files again.
Alan
-----
Radio Astronomy - the ultimate DX
Some of you are probably using multiple dongles with alternating
applications as well.
Regarding the frequency correction, I put a sticker on each dongle and
wrote the ppm value on it.
However manually setting the value in each application is still annoying.
So I used rtl_eeprom to write the value into the product-ID with the
following format: "RTL%+dppm" resulting in sth. like this: RTL+87ppm
I'm not sure if this is the best way to do it, but this approach works
without changing librtlsdr.
Another option might be storing the value in a non-used eeprom
location and adding get/set functions to librtlsdr.
Is it possible to write arbitrary values to unused eeprom locations
without fucking up the realtek eeprom handling? Do you think this
would be a better way?
I'd like to hear your comments on this.
It would be awesome if we could find a solution that many existing
applications could incorporate.
(Of course the ppm value still changes with temperature, but having a
base value is still closer to the truth than 0ppm I'd say.
I measured the offset directly after grabbing samples for 20 minutes
at room-temperature and jitter is <1ppm.)
Best regards,
Hunz
Hi all,
One of the designers of the R820T tuner has recently been posting on the
ultra-cheap-sdr group, and has kindly supplied a map of the R820T registers
for private use only within the SDR community. He has asked that it not be
posted on any website, but only be forwarded around privately.
To that end, if anyone would like a copy of this spreadsheet and would be
willing to likewise not publish it on the web, let me know off-list and I'll
send it to you.
There's not a huge amount in the way of explanations, but it lists all the
registers and a very brief description of what they do.
Cheers,
Adam.
Hello
I have been fighting to compile the gr-osmosdr package in my osx
These are the minor fixes I had to do:
1- Change in Cmakelists.txt: find_package(Boost COMPONENTS thread system),
If thread and system is not included then there are linking problems.
Although I see that this was removed recently...
2- cmake -DCMAKE_INSTALL_PREFIX=/opt/local (so it is installed together
wit my ports intallation, this is really optional)
3- Before compiling I manually edit CmakeCache.txt, and change all the
references of /usr/lib/python to /opt/local/lib/python. If not it links
agains the system python instead of the ports's python!
4- Add this line in my .bashrc so python can find the package
export PYTHONPATH="/opt/local/lib/python2.7/site-packages/"
I am aware that this is not the most elegant way to solve the problem but
is the only one that I was able to come up. Hope it helps
Regards
I am also having the rtl_fm scanning bug which was first reported in
http://lists.gnumonks.org/pipermail/osmocom-sdr/2013-February/000485.html
The scanning mode in rtl_fm hangs during the re-tuning process. This
makes it impossible to use rtl_fm in scanning mode. I am using Ubuntu
12.10 with libusb 2:1.0.12-2, the latest git master version of rtl-sdr,
and an Elonics E4000 (Realtek, RTL2838UHIDIR).
Here are the steps to reproduce:
1. Find some frequency FREQ_NOISE that is not in use, and some frequency
FREQ_SIGNAL which is in use constantly (i.e., like a commercial FM
station). Find an appropriate squelch value SQUELCH which will stop
FREQ_NOISE but pass FREQ_SIGNAL.
2. rtl_fm -f ${FREQ_NOISE} -l ${SQUELCH}. The program should not pass
any audio, but it will exit cleanly with ^C.
3. rtl_fm -f ${FREQ_SIGNAL} -l ${SQUELCH}. The program should pass audio
and exit cleanly with ^C
4. rtl_fm -f ${FREQ_SIGNAL} -f ${FREQ_NOISE} -l 0. The scan will pause
on the first channel and pass audio.
5. rtl_fm -f ${FREQ_NOISE} -f ${FREQ_SIGNAL} -l ${SQUELCH}. The program
will not output any audio, even though the first frequency is squelched
out and the scanning function should skip immediately to the second
frequency. Additionally, it will not exit if sent a SIGINT with ^C, and
it must be killed with a SIGKILL.
I've made a stack trace of this behavior. The program hangs very
consistently at the same location each time:
http://pastebin.com/wzE09MCi
Thread 1 (the USB buffer reading thread) hangs while waiting for the
data_write mutex lock in rtl_fm.c:642. I presume the thread has
exhausted its supply of data and isn't getting any more.
Thread 2 is slightly more interesting, because it hangs during the
libusb system calls within the tuning function rtlsdr_set_center_freq()
in librtlsdr.c:796. My guess is that it's making a blocking call that
never returns.
Can anyone else reproduce this bug?
Hi All,
Can anyone point me in the direction of a place I can go to submit patches?
I fixed a bug in CMake for gnuradio-osmosdr that stopped the build on my system.
Best,
Mike
I'm using rtl_fm in a scanning (nbfm) situation, and even with the antenna input disconnected and terminated, I get a burst of noise that sounds like a squelch tail maybe once each scan cycle. They're a little over 1 second apart. I've tried setting the squelch up to 10000 where I don't get signals anymore, but I still get the noise.
I discovered that if you scan and have the output be a raw audio file, nothing gets recorded when nothing breaks squelch. This makes time-lapse recordings where all the pauses are taken out. Very nice, except for the noise bursts.
I'm using:
#!/bin/sh
rtl_fm -N -S -l 132 -p 102 -f 854040000 -f 854240000 -f 854315000 -f 854415000 -f \
854490000 -f 854540000 -f 855165000 -f 855240000 -f 858790000 -f 867350000 \
-f 867715000 /tmp/`date +"%Y-%m-%d_%H%M.raw"`
and recorded overnight, but I mostly got noise bursts.
Alan
-----
Radio Astronomy - the ultimate DX
Hello!
This is a minor issue, but may lead to some misunderstanding (and seach
failures) in future.
The package to correct IQ imbalance is registered at http://cgit.osmocom.org
as gr-iqbal but project name set in line 24 of toplevel CMakeList.txt is gr-
iqbalance.
Which name should be used while building packages, etc.?
BTW: Is there any homepage for gr-iqbal/gr-iqbalance?
Wojciech Kazubski
