Hi Marc, if in doubt, keep the list in. If it's too specific, someone will complain (or not. Simply sorting away mails you don't care about is what you need to do when using a mailing list).
> I don't get what you say yet. What do you mean with "tell the hackrf > to re-tune"? The only way that I see to do this is by software (using > gnuradio). Well, but you *don't* retune the HackRF by generating a chirp in software. > This is were I get lost. In my opinion, if for example the Osmocom > Source sees the band from 900MHz to 920MHz is because the center > frequency of the block is set to 910MHz (and sample rate of 20MHz), yes, > so I just have to make this parameter change (center freq) to see the > "unknown signal" you're talking about, yes, > because the hackrf can see much further in the spectrum. Isn't > changing the center frequency of the Osmocom Source equivalent to > "tune the hackrf" ? It is. But it has nothing to do with generating a chirp. Let me ask this a tenth time: What were you planning to do with your chirp? Best regards, Marcus On 01/13/2017 06:59 PM, Marc Pàmies Massip wrote: > Okay, I am new using the mailing list and I didn't know if I had to > answer you individually or by doing a broadcast. > > I don't get what you say yet. What do you mean with "tell the hackrf > to re-tune"? The only way that I see to do this is by software (using > gnuradio). >> You can also think about it this way: The Osmocom source only gives >> you what it sees. Those are the 20 MHz. There's nothing in the world >> that you could multiply to something that doesn't contain the unknown >> signal you're interested in to make it show you that unknown signal. > > This is were I get lost. In my opinion, if for example the Osmocom > Source sees the band from 900MHz to 920MHz is because the center > frequency of the block is set to 910MHz (and sample rate of 20MHz), so > I just have to make this parameter change (center freq) to see the > "unknown signal" you're talking about, because the hackrf can see much > further in the spectrum. Isn't changing the center frequency of the > Osmocom Source equivalent to "tune the hackrf" ? > > Marc. > >> On 13/01/2017 13:34:59, Marcus Müller <marcus.muel...@ettus.com> wrote: >> >> Hi Marc, >> >> I'll be taking the list back into the loop, if that's OK with you; I >> think there's general knowledge in here that we might want to share. >> >> > Correct me if I am wrong. If I want to find, let's say, the 10 >> strongest signals in a rf-band which is longer than the BW that my >> SDR peripheral can look at, I have to tune the device to inspect all >> the band step by step. >> >> Exactly! >> >> > And the way to implement it in GNUradio is using a Multiply block >> with two inputs: one coming from the Osmocom Source (real life >> spectrum) and another coming from a Signal Source (sinusoid generated >> by software), so that the output would be a part of the GSM band >> tuned at the frequency of the sinusoid. Am I right? >> >> No! >> >> As I said: >> That chirp is *inside GNU Radio*, ie. it's a >> sequence of numbers inside your computer. The GSM signals are on the >> air. So what you need to do to combine the chirp with these signals is >> one of >> >> 1. Use some sort of SDR device to convert the >= 45MS/s stream >> containing the linear chirp from digital domain to actual analog signals >> in order to mix the two, or >> 2. Use some sort of SDR device to convert the >= 45MHz of analog GSM >> signals to the digital domain in order to multiply the two. >> >> Either way, you need something that can deal with 45 MS/s! >> >> You can also think about it this way: The Osmocom source only gives >> you what it sees. Those are the 20 MHz. There's nothing in the world >> that you could multiply to something that doesn't contain the unknown >> signal you're interested in to make it show you that unknown signal. >> >> >> So, what you need to do is tell the HackRF to re-tune. >> >> Best regards, >> Marcus >> >> On 01/13/2017 11:24 AM, Marc Pàmies Massip wrote: >>> Hi Marcus, >>> >>> In that case (GSM band of 20MHz) I wouldn't have to tune the hackRF >>> because just by setting the Center Frequency in the middle of the >>> band I would be able to see all the spectrum... When I said "sweep" >>> before I meant inspect/analyse a part of the spectrum (for example >>> using a block that can detect peaks or some kind of threshold). >>> >>> Correct me if I am wrong. If I want to find, let's say, the 10 >>> strongest signals in a rf-band which is longer than the BW that my >>> SDR peripheral can look at, I have to tune the device to inspect all >>> the band step by step. And the way to implement it in GNUradio is >>> using a Multiply block with two inputs: one coming from the Osmocom >>> Source (real life spectrum) and another coming from a Signal Source >>> (sinusoid generated by software), so that the output would be a part >>> of the GSM band tuned at the frequency of the sinusoid. Am I right? >>>> >>>> On 12/01/2017 20:55:46, Marcus Müller <marcus.muel...@ettus.com> wrote: >>>> >>>> Hi Marc, >>>> >>>> >>>> On 12.01.2017 20:14, Marc Pàmies Massip wrote: >>>>> I want to make sure that I can inspect the whole GSM band. >>>> >>>>> The reason is that I want to passively detect pedestrians by means >>>>> of their cellphones emissions, but those emissions can be at any >>>>> part of the spectrum. As I have no information of which >>>>> frequencies are going to be used to establish communication with >>>>> the BTSs I have to sweep the whole band. >>>> Why do you need to *sweep*? You get 20 MHz at once, containing all >>>> the channels therein. Let's simplify our problem and assume that >>>> *all* GSM happens within these 20 MHz. >>>> >>>> So, what do you mean with "sweep"? What is the reason you sweep, >>>> what is its advantage? >>>> >>>> Cheers, >>>> Marcus >>>> >>>>> Is this what you were asking? Maybe it sounds strange to you >>>>> because the way I am trying to achieve this is not the right one? >>>>> >>>>> Marc. >>>>>> >>>>>> On 12/01/2017 20:05:32, Marcus Müller <marcus.muel...@ettus.com> >>>>>> wrote: >>>>>> >>>>>> Hi, >>>>>> >>>>>> > Starting from the fact that by multiplying a signal by >>>>>> cos(2*pi*f*t) you are displacing it f Hz in the frequency domain, >>>>>> my idea was to center the Osmocom Source at 835MHz (with a sample >>>>>> rate of 20MHz it would cover the range 825M-845M) and evaluate >>>>>> that part of the spectrum. >>>>>> >>>>>> That sounds right. You could, for example, simply connect the >>>>>> osmocom source to a Qt GUI Waterfall sink and watch the GSM >>>>>> channel activity "scroll by". >>>>>> >>>>>> > Then, to change the center frequency of the band to be analysed >>>>>> I supposed that I had to multiply the output of the Osmocom >>>>>> source by a sinusoid, but now you are making me doubt jeje. >>>>>> >>>>>> So, *why* do you want to do that? I think there's probably a very >>>>>> good idea behind that, but I'm not quite getting the bigger >>>>>> picture. What is it that you want to *achieve*? >>>>>> >>>>>> Best regards, >>>>>> Marcus >>>>>>> >>>>>>> In the first email I was trying to do it multiplying the output >>>>>>> by a sinusoid of frequency 1Hz, then 2Hz, then 3Hz, .... until >>>>>>> 45MHz, and then it would have 1Hz again to start over. But with >>>>>>> your answer I realised that it was not possible to change the >>>>>>> frequency of a sinusoid generated by a Signal Source block. >>>>>>> >>>>>>> Then I thought that you were proposing to multiply it by a chirp >>>>>>> because somehow it is a sinusoid which frequency increases >>>>>>> progressively... But I am wondering if it would work now. >>>>>>> >>>>>>> Do you know of any way to do this discrete step process using >>>>>>> some GNUradio functionalities? I mean a way to do some kind of >>>>>>> radio frequency scanner. >>>>>>> >>>>>>> Thank you again, >>>>>>> >>>>>>> Marc. >>>>>>>> >>>>>>>> On 12/01/2017 19:33:36, Marcus Müller >>>>>>>> <marcus.muel...@ettus.com> wrote: >>>>>>>> >>>>>>>> Exactly, you tune the HackRF to the lower part, then tune it to >>>>>>>> the next part, and so. That's a discrete step. You get e.g. 20 >>>>>>>> MHz at once, and you decompose these into channels. Why would >>>>>>>> you want to multiply it with the chirp? What is the benefit >>>>>>>> you're trying to achieve by doing so? >>>>>>>> >>>>>>>> >>>>>>>> On 12.01.2017 19:25, Marc Pàmies Massip wrote: >>>>>>>>> Yes! Sorry, my answer was not complete. I am using a SDR >>>>>>>>> peripheral (HackRF) with the appropriate antenna to listen the >>>>>>>>> GSM bands. But as it is not possible to look at the whole >>>>>>>>> spectrum at once to find the biggest peaks, I want to do it by >>>>>>>>> parts. So first I start looking at the lower frequencies and >>>>>>>>> then go up progressively in the frequency domain until the end >>>>>>>>> of the GSM band. >>>>>>>>> >>>>>>>>> I think that the maximum sample rate this hardware can deal >>>>>>>>> with is 20MHz. So I just want to get 20MHz with the device all >>>>>>>>> the time, and displace this 20MHz multiplying the chirp with >>>>>>>>> the output of the Osmocom Source Block (which outputs whatever >>>>>>>>> the HackRF captures). Am I missing something? >>>>>>>>> >>>>>>>>> Marc. >>>>>>>>>> >>>>>>>>>> On 12/01/2017 19:12:49, Marcus Müller >>>>>>>>>> <marcus.muel...@ettus.com> wrote: >>>>>>>>>> >>>>>>>>>> Hi, >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On 12.01.2017 19:06, Marc Pàmies Massip wrote: >>>>>>>>>> > >>>>>>>>>> > Regarding to your last question, I'm trying to make a >>>>>>>>>> GSM-sensor to >>>>>>>>>> > detect the signals sent from mobile stations (MS) to base >>>>>>>>>> stations >>>>>>>>>> > (BTS). I should detect phones that are not currently being >>>>>>>>>> used, but >>>>>>>>>> > the signals sent by these are really weak. For this reason >>>>>>>>>> I want to >>>>>>>>>> > previously scan the downlink channel (signals sent from BTS >>>>>>>>>> to MS are >>>>>>>>>> > easier to detect) to find the frequencies of the most >>>>>>>>>> powerful BTSs, >>>>>>>>>> > and with this I would have an idea of where the weakest >>>>>>>>>> signals sent >>>>>>>>>> > by MS could be. So the chirp will be used to modulate in >>>>>>>>>> order to >>>>>>>>>> > sweep the whole GSM-band. At the moment I am just starting >>>>>>>>>> so there is >>>>>>>>>> > not much to say... but that would be the idea. I don't >>>>>>>>>> really know if >>>>>>>>>> > there are better ways of scanning a wide band using >>>>>>>>>> GNUradio, but your >>>>>>>>>> > chirp idea sounds great. >>>>>>>>>> > >>>>>>>>>> I still don't understand. That chirp is *inside GNU Radio*, >>>>>>>>>> ie. it's a >>>>>>>>>> sequence of numbers inside your computer. The GSM signals are >>>>>>>>>> on the >>>>>>>>>> air. So what you need to do to combine the chirp with these >>>>>>>>>> signals is >>>>>>>>>> one of >>>>>>>>>> >>>>>>>>>> 1. Use some sort of SDR device to convert the >= 45MS/s stream >>>>>>>>>> containing the linear chirp from digital domain to actual >>>>>>>>>> analog signals >>>>>>>>>> in order to mix the two, or >>>>>>>>>> 2. Use some sort of SDR device to convert the >= 45MHz of >>>>>>>>>> analog GSM >>>>>>>>>> signals to the digital domain in order to multiply the two. >>>>>>>>>> >>>>>>>>>> Either way, you need something that can deal with 45 MS/s! >>>>>>>>>> >>>>>>>>>> Best regards, >>>>>>>>>> Marcus >>>>>>>> >>>>>> >>>> >>
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