osmocom-sdr

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906 discussions

Updated gr-osmosdr for GNU Radio 3.7
by Tom Rondeau 25 May '13

25 May '13

Not sure if anyone else had worked on this, but I couldn't find anything. I updated gr-osmosdr to work with GNU Radio 3.7 (currently the next branch). You can find it here: https://github.com/trondeau/gr-osmosdr I didn't redo the code to be in the 3.7 API style, just made sure that it could build off gnuradio and run properly. Tom

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Regarding offset tuning in rtl_fm.c - the math
by Aaron Rossetto 25 May '13

25 May '13

Hi all, I recently got a Raspberry Pi and an RTL2832 USB card and have been successful in compiling rtl-sdr and running the associated examples, piping the data up into LabVIEW for analysis with their Demodulation Toolkit. I'm a little weak on the signal processing math knowledge here, so I was wondering if someone could explain the math behind the offset tuning code in rtl_fm's optimal_settings() function. It looks like the function takes the desired center tuning frequency and calculates an integer decimation ratio based on a "capture rate" near 1 MHz and the desired final sampling rate. Then the center frequency is offset by a quarter of the capture rate, and this and the capture rate are used to program the radio. Then in the receive callback, the I/Q data is shifted 90 degrees in rotate_90(). At this point, the I/Q data represents (I presume!) the spectrum around the original desired center frequency and at the original sample rate. How do I get, mathematically speaking, from the oversampled I/Q data centered at the offset frequency to *my* desired center frequency and sample rate? I'm especially curious as to the effect of the frequency offset using that particular value (capture rate/4) and what role the rotation plays in the transformation. Thanks, Aaron

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rtl_fm scanning mods
by Alan Corey 24 May '13

24 May '13

This diff below is actually 2 changes. When scanning it will print the frequency to stderr every time something breaks squelch. When searching/scanning a range it logs active frequencies into a file in /tmp. Two notes: there's an extra \n at the start of each frequency announcement, that's to get around sox's output. If you use something like aucat that doesn't write to the console you don't need that. The file path should be ifdefed and an appropriate Windows path added. This diff was taken before my fix to the scanning step, which may change the context slightly. Alan *** rtl_fm_original.c Wed May 22 13:18:00 2013 --- rtl_fm.c Wed May 22 13:32:53 2013 *************** *** 76,82 **** --- 76,86 ---- static int *atan_lut = NULL; static int atan_lut_size = 131072; /* 512 KB */ static int atan_lut_coef = 8; + static int f_ann = 0; /* freq announced */ + static int searching = 0; + static FILE *flog; /* frequency log */ + struct fm_state { int now_r, now_j; *************** *** 587,592 **** --- 591,603 ---- return; } sr = post_squelch(fm); + if ((sr > 0) && (f_ann == 0) && (fm->freq_len > 1)) { + fprintf(stderr, "\n%f\n",(double)fm->freqs[fm->freq_now]/1000000.0); + f_ann = 1; /* reset next hop */ + if (searching > 0) { + fprintf(flog,"%f\n",(double)fm->freqs[fm->freq_now]/1000000.0); + fflush(flog); + } if (!sr && fm->squelch_hits > fm->conseq_squelch) { if (fm->terminate_on_squelch) { fm->exit_flag = 1;} *************** *** 609,614 **** --- 620,626 ---- /* ignore under runs for now */ fwrite(fm->signal2, 2, fm->signal2_len, fm->file); if (hop) { + f_ann = 0; freq_next = (fm->freq_now + 1) % fm->freq_len; optimal_settings(fm, freq_next, 1); fm->squelch_hits = fm->conseq_squelch + 1; /* hair trigger */ *************** *** 676,681 **** --- 688,696 ---- stop[-1] = '\0'; step = strchr(stop, ':') + 1; step[-1] = '\0'; + flog = fopen("/tmp/freqlog.txt","a"); + if (flog != NULL) + searching = 1; for(i=(int)atofs(start); i<=(int)atofs(stop); i+=(int)atofs(step)) { fm->freqs[fm->freq_len] = (uint32_t)i; ----- Radio Astronomy - the ultimate DX

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Weird rtl_fm bug
by Alan Corey 24 May '13

24 May '13

This only affects scanning, or specifically searching a range of frequencies. I could hear it in the example from usage -f 118M:137M:25k. For some reason the step changes as the loop executes so the frequencies look like: 118950000 118975000 119000000 ok to here 119257000 119282000 119307000 119332000 119357000 119382000 119407000 119432000 119457000 119482000 119507000 119532000 119789000 119814000 119839000 119864000 The frequencies should be at 25 KHz intervals. I don't have a diff because I have several other changes in my version, but my frequency_range() now looks like: void frequency_range(struct fm_state *fm, char *arg) { char *start, *stop, *step; int i; int frst, frstp, frdelta; start = arg; stop = strchr(start, ':') + 1; stop[-1] = '\0'; step = strchr(stop, ':') + 1; step[-1] = '\0'; frst = (int)atofs(start); frstp = (int)atofs(stop); frdelta = (int)atofs(step); fprintf(stderr,"start: %i, stop: %i, step: %i\n",frst,frstp,frdelta); // step was changing here somehow: // for(i=(int)atofs(start); i<=(int)atofs(stop); i+=(int)atofs(step)) for (i=frst; i<=frstp; i+=frdelta) { fm->freqs[fm->freq_len] = (uint32_t)i; fm->freq_len++; } stop[-1] = ':'; step[-1] = ':'; } I added the fr* variables and used them in the loop. It sounds better now that none of the frequencies are off. I'm also logging and those frequencies look OK. Alan ----- Radio Astronomy - the ultimate DX

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RTL SDR LNAs
by Jonathan Rawlinson 23 May '13

23 May '13

Hello All This is the first time I have posted on this list, sorry if I have done it wrong I would like to use a line powered "cheap and nasty" LNA with an RTL dongle. E.g. http://www.amazon.co.uk/Satellite-Signal-Amplifier-Booster-electrosmart%C2%… This may seem a like stupid question (I will ask it anyway) but will the dongle need protecting from the 18V going down the antenna line. I have seen some diagrams with protection and some without. If protection is required, has anyone got any suggestions on how I should do it??? Many thanks Jonathan, M0ZJO

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osmosdr block
by laurent 22 May '13

22 May '13

Hi all, I need some help to resolve my problem with GNURADIO. I Built and installed rtl-sdr and it works well with the dongle terratec. Built and install also the osmosdr package, but when I open grc the block sources rtl does'nt appear. Any ideas? GNUradio for debian package v.3.5.3.2-1 installed. Best regards Laurent

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rtl_fm....external interface...any way?
by Favati 19 May '13

19 May '13

Hi there! I would like to know if is it possible to change the freq. of rtl_fm "on the fly" without cloning the process and restart it with a a different freq. parameter. Any idea?

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RTL-SDR component for REDHAWK SDR
by Michael Ihde 19 May '13

19 May '13

I've recently developed a RTL-SDR component for REDHAWK that uses the RTL-TCP server. https://github.com/Axios-Engineering/acquisition-components I'm guessing that this mailing list is the correct address to use for this component to be listed on the "Known Apps" page for the RTL driver. ~Michael

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FW: A question on osmoSDR new version
by LD Zhang 13 May '13

13 May '13

From: LD Zhang [mailto:ldz10565@gmail.com] Sent: Monday, May 13, 2013 2:23 PM To: 'osmocom-sdr(a)lists.osmocom.org' Subject: A question on osmoSDR new version Hello, I am very interested in the new osmoSDR that has 4MS/s rate and a 14bit ADC. Is this new version available for purchase? Thanks, LD

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Re: Raspberry Pi based remote SDR head
by Simon PurplePlaNET 13 May '13

13 May '13

Ah, OK - I've got you. You also need to run the script once you have launched rtl_tcp using the command in step 3) below. The simplest way to do this would be to add a step: 6) Sign in to rPi with a new terminal session, leaving the old one open for now. cd to the directory where you created the script and then run it using this command: ./rtl-robot (or whatever you called the script) You could run the script from the same terminal that you launched rtl_tcp from if you used & to force rtl_tcp to detach from the console and run in the background. I'll edit the comments on the script to make that a bit clearer... Thanks! Simon ----- Original Message ----- From: "Favati" <smile_k(a)libero.it> To: osmocom-sdr(a)lists.osmocom.org Sent: Saturday, 11 May, 2013 20:14:36 GMT +00:00 GMT Britain, Ireland, Portugal Subject: Re: Raspberry Pi based remote SDR head > Could you describe exactly the steps you have taken? 1) installed wiringpi (and tested as described on the developer site) 2) created your script 3) launched this command: stdbuf --output=0 rtl_tcp -a 192.168.2.15 -p 1234 > rtl.data 4) used sdrsharp to connect to my raspberry (192.168.2.15, and it connect ok, i can use sdrsharp ok) 5) nothing is displayed on the console of my raspy except the first 2 lines of rtl_tcp output The rtl_data is created ok and looking inside that file i can see the normal output of "rtl_tcp" (set freq blablablabla, etc...) At the moment i've taken another approach...i've patched the rtl_tcp.c to set the gpio directly...i'll post my "project" asap somewhere...

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