osmocom-sdr

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904 discussions

RTL2832 questions
by Jeff Gustafson 08 May '12

08 May '12

Hi all, First of all, props to the person that found out how to put the RTL chip into a SDR compatible mode! I've been wanting to play around with SDR and, specifically, P25 for a while now. Finally an inexpensive way to get my feet wet. My question is probably a bit of a noob question. I have successfully received a broadcast FM radio station with the RTL dongle. The problem is that I can't seem to decode anything else. I tried to receive some ham radio (NFM) transmissions from my radio and I didn't get any sound. The white noise blanked out, the scope in gnuradio spiked up, but no real demodulation. Would someone be willing to share a .grc file they know will decode NFM with the gr-osmosdr/rtl-sdr driver? I tried taking some files that used the USRP driver and swapping out the USRP driver with the osmosdr/rtl driver, but no go. Could it be that I don't have all the sampling rates and decimation rates set correctly? ...Jeff

1 1

Patch for Compro U680F support.
by Marek Kroemeke 03 May '12

03 May '12

Hi guys, Unclear in what format you require patches - but I bought Compro U680F 2 days ago, it has the E4000 chipset and it only required adding usb id in, so as requested in docs - sending a small "patch" that makes it work :-) regards, Marek Kroemeke

2 1

Detach kernel driver
by Michal Demin 24 Apr '12

24 Apr '12

Hello, Attached are 2 patches: 1 - Try to detach kernel driver from device, when kernel driver present. 2 - add rtl_tcp binary to gitignore. Michal Demin

2 5

RTL-SDR ghost signal at center frequency & hangs in GR spectrum view
by Benedikt Heinz 20 Apr '12

20 Apr '12

Hi everyone, can someone explain to me, what the origin of the ghost signal close to center frequency is? It can be seen at [1] and [2] - both are EzTV668 with no antenna connected. It seems to me, that the higher the frequency, the more one can see the "burst-like" nature of this signal. Is this some mixer artefact from the E4k tuner? The best workaround is probably tuning a bit off the actual target frequency and using frequency xlate? Also, in [3] (german) the blind spot at 0Hz due to the coupling capacitors between E4k & RTL is mentioned. Is it possible to replace the capacitors with 0-Ohm resistors to work around this issue, or will this cause other unwanted side-effects? Or does this make no sense at all since one should always tune a bit off and use xlate due to the ghost signal? I guess it should also be possible (w/ some hot glue & wires) to insert some jumpers (like OsmoSDR) instead, so one can use the ADCs directly for LF/MF with some extra analog stuff? Regarding the OsmoSDR source - I also gave the RTL-source from gr-baz a try and noticed, that with averaging enabled in the spectrum view in GR, the top-block GUI usually won't react to user input any longer when using OsmoSDR, but this doesn't happen with the gr-baz RTL source, although I used the same sample rate in both cases. Does anyone understand why it doesn't hang with the gr-baz source? Thanks for your answers! Regards, hunz [1] http://hackdaworld.org/~hunz/rtl-sdr/wo_ant_2m_osmo.png [2] http://hackdaworld.org/~hunz/rtl-sdr/wo_ant_70cm_osmo.png [3] http://www.mikrocontroller.net/topic/253371#2610540 -- Benedikt Heinz hunz(a)jabber.berlin.ccc.de

3 2

OsmoSDR - they're on final approach
by Christian Daniel -- maintech GmbH 19 Apr '12

19 Apr '12

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi everybody, just as a short heads up: The new boards have arrived and the first batch of 20 is assembled. Since we did changes to the layout we will verify them before we do the other 80. This should take no more than a few days. Stay tuned! BTW: The new pre-amp/lnb really does add 18dB :) Best regards, Christian - -- - --------------------------------------------------- | maintech # Dipl. Inf (FH) Christian Daniel | | GmbH ### Otto-Hahn-Str. 15 · D-97204 Höchberg | - --------------------------------------------------- | AG Würzburg, HRB 8790 Tax-ID DE242279645 | - --------------------------------------------------- | http://www.maintech.de cd(a)maintech.de | - --------------------------------------------------- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJPkBrEAAoJEHkgzUIsAWritBgH/RqDZuLRLQ/22msTdvZ+EIqk 6Y98xDBrDcXSkTSsFBQvLwdKANUxxi3dVvTjknBw3lnrWzT8fo2uVMg97c/R6Eov fGOvALbXckgrmvz0n/IZdROu8x38zs/ro0uweN0oxb14+U/2CW5VVeJusqcQoBL6 Ug4XAtzXpyR04pmjjq6jzxtsmsXuv42KToG7R9UvkiNz8WXhxlaaUmA+ccJGM+8+ FCITzYY9ZMfFo2IekXDGkZNsKwux37B8cQxYIlcSlPxlSrPzusFyyqEq2AmM1iIn SbuRnmjzeUQbsgGVINmVP1B3EDOczeYWyeKC/5myXbr+Ogpp9/PD9K9aJG/sKYM= =KY1W -----END PGP SIGNATURE-----

1 0

Real-time DRM+ receiver chain using the NOXON stick
by Feilen, Michael 19 Apr '12

19 Apr '12

Dear Osmocon-SDR People, Thank you so much for providing the information on the RTL-SDR USB sticks on your webpage! I've used the stick to get a DRM+ receiver implementation running and the stick seems to work quite well: http://www.youtube.com/watch?v=zeGs7CQlvRg I've had to twiddle around with the tuner parameters of the FC0013 to get it running stable. However, I've never reached more than 25 dB SNR for the in-band OFDM signal (which has a bw of 100 kHz and I'm resampling from 1 MS/s to 120 kS/s). I wonder if the tuner is the limiting factor or the RTL chip. With a resolution of 8 bit, I would have expected more. Hmm, maybe it's the phase noise of the tuner or the IQ correction routines of the RTL chip? Has anybody of you guys a meaningful measure for the quality of the different tuners for the RTL stick? I know that the E4000 supports a higher bandwidth but does it provide a better IQ signal with less distortion? Cheers, Michael

1 0

rtl-sdr with Compro Videomate U620F
by Simeon Miteff 12 Apr '12

12 Apr '12

Hi All The Compro Videomate U620F has the magic RTL2832+E4000 combination. rtl-sdr recognises it with the patch: https://gist.github.com/2362895 Regards, Simeon.

2 1

Buffer length in rtlsdr_wait_async
by Andrea Montefusco 08 Apr '12

08 Apr '12

Hi all, together with Oliver DL6KBG (that really provides me with all the hardware needed, thanks !), we are attempting to write a server suitable for use with ghpsdr3-alex SDR software. A first attempt using the a home built code was quite successfully, albeit some defect is yet there. Now we are trying to use the librtlsdr: first off, many thanks to developers. We are stucked into rtlsdr_wait_async that is using a fixed quite large buffer, as per #define BUF_LENGTH (16 * 16384) now that is quite inconvenient in ghpsdr3-alex, because, at low sample rate (250000) we use, we are unable to cope with the large delay that this large buffer introduces. So, just as crude workaround, we simply patched the value into the lib. What would be ideal is an additional parameter in rtlsdr_wait_async that allow us to reduce the buffer to a more suitable size for our needs. Thanks in advance *am* --------------------------------------------------------- Andrea Montefusco iw0hdv http://www.montefusco.com tel: +393356992791 fax: +390623318709 ---------------------------------------------------------

2 1

Tuner performance for rtl-sdr
by Mathias Coinchon 05 Apr '12

05 Apr '12

Hi, Does anybody have some hints, experiences on the performance difference (filtering, sensitivity, IQ imbalance, DC offset,..) between fc0012, fc0013 and e4000 tuners ? I could not get my hands on an e4000 yet but just fc0012 and fc0013. On FM band I see quite a number of mirror images from strong signals. Mathias

1 0

Re: rtl-sdr with airprobe
by schwandre＠gmx.net 02 Apr '12

02 Apr '12

> I'd like to know what was the reasoning behind that statement ? > To me it shows a deep lack of understanding on how that script works ... the reason for this statement was, that i read somewhere, that the example-file was recorded with 1,8 MS/s and decimation of 174. yes, you are right, i don't know how that script works, i read the sources and understood maybe 5% of it, because this is all really new for me, as i am not a professional and my last programm i wrote, was for the 6510 about 20 years ago.... now i did some more readings and found, that to have needed bandwith of 200 khz with 1,8 MS/s is a decimation rate of 9 ? decimation=MS/bw ? guess i have to read a lot more, thanks for your info! -- NEU: FreePhone 3-fach-Flat mit kostenlosem Smartphone! Jetzt informieren: http://mobile.1und1.de/?ac=OM.PW.PW003K20328T7073a

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