October 2013 - osmocom-sdr - lists.osmocom.org

Complex FIR and Stereo support for rtl_fm
by Miroslav Slugeň 12 Nov '14

12 Nov '14

Hi again, I am working on my own SDR project for Stereo FM radio support, but i would like to also improve quality for rtl_fm application, i made unoficial patch to add: Complex FIR - to filter strong signals close to wanted signal Real FIR - to filter pilot from FM Stereo FIR Stereo Deemphasis AGC support - it can give better resolution of IQ data Some other improvments in FM radio code. All FIR filters has 3 possible variants, simple, LUT, SSE2 instricts, of course SSE is the fastest one and it should works on Intel Atoms, but not on ARM. Feel free to use any part of code in any of you programs, I know that this code is little to much to add it into rtl_fm, but maybe it could somebody help to recieve HW stereo FM radio. Speed of SSE code is much better than anything you can get around here, on Core i7 it consume only 5% of one CPU, so i could demodulate at least 80 channels at the same time in stereo quality of course. I tried this code only on AMD64 and GCC Linux, so i am not sure if it can be compiled under windows. -- Miroslav Slugeň +420 724 825 885 Teramos Multimedia s.r.o.

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rtl_tcp problem or not?
by Favati 25 Feb '14

25 Feb '14

Hi there! I'm using a dongle on a raspberry + rtl_tcp and sdrsharp on another machine (quad core.... 3gb ram...good machine!) The problem occour at 00:57 http://www.youtube.com/watch?v=4E2MPfEzEi8 and at 1:34 in this video: http://www.youtube.com/watch?v=8snz1wQSRpw If i stop and start sdrsharp, it works ok for some minutes...then the problem is up again! No errors appear on the console of raspberry/rtl_tcp I'm not able to understand if it's a problem of rtl_tcp,raspberry or whatelse... Things i've tryed: 1) Changed the samplerate 2) Changed the raspberry (tested tp1/tp2 too...getting 4.98v!!!) 3) Changed the dongle 4) Updated sdrsharp The dongles tryed work ok on a pc I've no more idea.... Anyone can help me? PS: If someone know a program that works in linux and is similar to sdrsharp AND CAN INTERFACE TO A REMOTE RTL_TCP...

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odd results working at 250ksp/s
by David Jacobowitz 10 Feb '14

10 Feb '14

Hi, I've been working on a project the involves tuning VOR signals. They are narrow band signals. > 25 kHz. For that, the wide bandwidth of the RTL dongles isn't that helpful to me. (and actually a hindrance when two signals are inside the sample range but widely different strengths) Anyway, the lowest I can get my dongles (R820T) to go is 250ksps, which is fine. I've been working at that frequency for awhile, but getting some strange results. For example, if I tune in to 116.8 MHz, which should be the OAK VOR, it works fine. But if I tune to 115.8 MHz, which should be the SFO VOR I get ... the OAK VOR. That is, there is a perfect copy of the OAK signal 1 MHz shifted down. If I switch the sample rate to 1.024Msps or 900ksps, I don't get this problem. I don't understand what is happening here. 1 MHz is an even multiple of 250kHz, so maybe I'm getting an image of OAK overpowering the relatively weaker SFO signal. But should there not be filters that manage this? I guess I was expecting that if the device is set to 250ksps, then it would "close down" filters appropriately to reject signals out of that band. But maybe the filters don't work properly below a certain sample rate? Like the rtl2832 can sample down to 250ksps, but the 820T tuner was not designed for it? Or perhaps I'm doing something wrong? Can I control the filters directly? I'm glad I find this issue because I was going nuts thinking my software had some mysterious bug. But I can reproduce this issue just with SDR# or whatever. :-) Regards. Dave J

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How to get IQ samples from multiple rtl-sdr dongles in a synchronized manner?
by Jiao Xianjun 02 Jan '14

02 Jan '14

Hi, I want to use multiple rtl-sdr dongles to do some multi-antenna experiments. Is it possible to read IQ samples from multiple rtl-sdr dongles in a synchronized manner? I already have a glance at dump1090 codes, which is a project using rtl-sdr to decode aircraft broadcasting ADS-B messages in 1090MHz. Seems that I should use rtlsdr_read_async() instead of rtlsdr_read_sync(), because that if rtlsdr_read_sync() is used, I have to call it multiple times sequentially. That looks not synchronized. But rtlsdr_read_async() function only accept one rtl-sdr device as input parameter, and it will be blocked after it is called. So seems that it also can't be used for my purpose directly. Also welcome any opinion on how to improve rtl-sdr lib/driver to support this feature. Thank you. BR Jiao Xianjun

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MiricsFlexiTV-MSI3101
by marzano 21 Nov '13

21 Nov '13

A quite good (AM/SW)/FM/DAB/DVB-T USB dongle. Mirics FlexiTV MSi3101 (two chips MSi001+MSi2500) http://www.mirics.com http://www.mirics.com/node/31 Data sheets available, register yourself at Mirics portal. RF Tuner: MSi001/MSi002 ( used by FUNcubrePro+ ?), seems better than R820T ADC and HiSpeed USB interface: MSi2500 . ADC 10 bit , better than 8 bit RTL2832U aDC. Windows binary software available: FMDABplayer, DVB_T decoder, Windows lib.dll and API doc. IO-DATA GV-TV100 stick sold on Japan . Stick, chips and dev board available from Mirics. Linux software at address http://cgit.osmocom.org/libmirisdr/ It seems project on stand-by . Can author Steve Markgraf comment ? Francesco

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I/Q data for dummies
by Skip Tavakkolian 31 Oct '13

31 Oct '13

I'm not an RF engineer and know enough of the physics of it to be dangerous. My approach to rtl-sdr is purely utilitarian -- i.e. using it to develop applications. The following tutorial, by Mikael Q Kuisma, on I/Q data was very useful to me and might benefit others on the list. http://whiteboard.ping.se/SDR/IQ -Skip

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RTL-SDR Error code -3
by Jonathan Rawlinson 30 Oct '13

30 Oct '13

Hello all I am trying to get the python wrapper "pyrtlsdr" working on Windows, it works fine on Linux The dongle works fine in SDR-SHARP.exe It imports correctly but prints the following error when I try to initialize the Dongle: Traceback (most recent call last): File "C:\Users\M0ZJO\Desktop\RA_Astro\FFTPrint Test.py", line 4, in <module> sdr = RtlSdr() File "build\bdist.win32\egg\rtlsdr\rtlsdr.py", line 60, in __init__ % (result, device_index)) IOError: Error code -3 when opening SDR (device index = 0) RTL_FM also returns the same error. Can anyone help? I would be very grateful! Many thanks Jonathan/M0ZJO

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rtl_fm.exe issue or an I doing something wrong?
by Chris Hanson 28 Oct '13

28 Oct '13

I just downloaded the RelWithDebInfo precompiled windows software that was posted on Oct 24th. I am using an E4000 dongle which has a PPM of +30. I am trying to listen to 424.175MHz and I'm using this: rtl_fm -p 30 -d 1 -N -o 4 -f 424.175M -s 16k -C|sox -r 16000 -t .raw -e signed-integer -b 16 -c 1 -V1 - -d everything is playing fine. I can hear 424.175MHz. The issue is that I'm hearing another station 50KHz higher on 424.225Mhz in addition to the frequency I want. So it looks as if it's not using a 16Khz filter. Am I doing something wrong or is there an issue with rtl_fm.exe? Thanks Chris

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rtl_fm stereo?
by Pete Ashdown 24 Oct '13

24 Oct '13

Tried searching on this and didn't find much. Is rtl_fm stereo capable? When I encode with lame's "-m s" flag the output is at half the sample rate (ie: speeded up). Do I need to feed it double the sample rate, or am I barking up the wrong tree entirely? Thank you.

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API for forwarding remote control commands
by Skip Tavakkolian 21 Oct '13

21 Oct '13

Hi, Since all DVB-T receivers come with an IR remote control, I'm wondering if there is an API that can be used to receive the remote commands? Thanks, -Skip

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