Oops, should say centered at 100Mhz* On Jul 11, 2017 3:41 AM, "Anon Lister" <listera...@gmail.com> wrote:
> Hey, > > So, a little DSP background. > ------ > > Keep in mind pretty much all the SDRs now output complex (I/Q) / > Quadrature samples. This means two things. Nyqust BW = Sample Rate, and > everything is centered at 0 frequency digitally. Basically, where you would > think of a bandwidth control before, use sample rate now. Bandwidth usually > refers to a filter applied to the sample_rate (remember, bandwidth=sample > rate) sized chunk of spectrum. > > The SDR takes that original spectrum (10M of complex bandwidth centered at > 90Mhz in your case, down converts it to baseband, and sends it to the PC. > GR is plotting [-5M, 5M] (but helpfully overlaying the original tuned > frequency for you, since you have told it where that is in the QT GUI sink.) > > Also, unlike your (probably) superhet recievers, most SDR devices, > including the hackrf are direct conversion. This type of receive has a > couple drawbacks over the superhet ones. (There are pros too usually > size/weight/power/cost.) One con is DC leakage. That is the bigger spike > you see at the center. You can avoid it by offset tuning. I think the ham > folks would call this a VFO. Basically it, in software, will take the > spectrum from a point not at 0, shift it down to 0, and bandpass filter it. > Then do the FM/AM/ec demod. (You can also simply overpower the spike with > your carrier, if possible, but the hackrf has a rather large amount of > leakage vs others so it's not always practical, and it would need to be at > the antenna power, not post digitization.) > > If you insist on using Windows I think SDRConsole might work a bit better > for you, and is probably setup to be a little more friendly to someone > coming into the SDR thing from a ham background or someone who is not very > used to a Linux environment. However setting it up requires using zadig, > but if you got it working with sdr#, it should already be setup. Also I'll > say if you want to do hammy things, like receive AM, N/WB FM, SSB, etc. > these software packages are what your looking for, not something like > gnuradio. They usually have the point and click VFO/offset tuning setup, so > you pick you modulation, click on the center, drag the box or enter the > bandwidth you want for the demod, and you get data. Gnuradio is more akin > to a box of wires, components, and tools you will need if you want to build > your own radio, and many pages of manuals for each independent piece. Its > an awesome tool if you want to experiment with building different kinds of > radios, perhaps a bit overkill or a bit much if you just want to use one. > (At least till you get your feet wet in the SDR world, and start thinking, > man wouldn't it be cool if sdr#/SDRConsole/gqrx could do XYZ, and then > realize GR provides you the tools to do just that.) > > I'll also mention there is a Pentoo live USB stick image you can download > and boot into with all the drivers and such ready to go for a Linux setup. > Just plug it in and boot off it. If you do try this the best (imho) Linux > version of the SDR#/SDRConsole radio receiver app flavor, is gqrx, which > should come on the Pentoo image by default. > > If you do keep playing with GR, you should sign up for the > discuss-gnuradio mailing list which is very active, and can help with some > of your gnuradio questions. > > ---- > So for your current setup: > > BW will control the digital bandpass filter on the hackrf. It will not do > what you want. Try setting that equal to the sample rate(samp_rate by > default), and changing the sample rate to something like 4M. From your FFT > it looks like you have possibly two weakish FM carriers visible, but your > bandpass is set to only a meg or two, so you might be missing some on the > side, that are higher power. > > You'll need to adjust the gain sliders. The help documentation(or see [1]) > should describe what they mean for the hackrf, of which there are three. > "RF gain" is a toggle for the rf amp. Leave this one off/0. The other two, > the bb and if gain I believe, you can play with, setting both to about 16 > should be ok to start, however I find setting the if gain to 32 and the bb > to about 4 seems to work better for me. > > > [1]https://www.reddit.com/r/hackrf/comments/49aa2i/using_ > gain_controls_with_osmocom_sourcesink_in/ > > -Anon > > On Jul 11, 2017 12:36 AM, "Jerry" <jster...@att.net> wrote: > >> Jake >> >> >> >> Thanks for the sound advice. I have had spectrum analyzers and learned >> early to be careful with nearby RF sources ☹ >> >> >> >> Right now I am getting a wide confluence of signals between 98.5 and >> 101.5 on the FFT. If it were my SA I would narrow the bandwidth to improve >> the signal resolution but on the Osmocom Source changing Ch0 Bandwidth from >> 10 Hz to 500 Hz doesn’t appear to change the FFT display noticeably. >> >> >> >> Attached is a picture. >> >> >> >> Jerry NY2KW >> >> >> >> >> >> *From:* HackRF-dev [mailto:hackrf-dev-boun...@greatscottgadgets.com] *On >> Behalf Of *Gavin Jacobs >> *Sent:* Monday, July 10, 2017 6:22 PM >> *To:* hackrf-dev@greatscottgadgets.com >> *Subject:* Re: [Hackrf-dev] Is my new (old) HackRF Deaf? >> >> >> >> Jerry, >> >> Learning how to use Ubuntu, and Gnu, and HackRF is a challenge! I went >> down that path about a year ago. The issue you describe hits every new >> user. When you are running GNU radio, you have to turn up the IF gain to >> about 40 - it defaults to 0. Also, turn up the BaseBand gain to about 30. >> Leave the RF gain at 0 (that setting is confusing; a value of 0 just means >> the RF LNA is left off; 14 means it is on; but you rarely need it on). >> >> >> >> Also, a word of caution. Since you are a ham, you likely have an HT or a >> base station. You have to take care to never exceed the maximum field >> strength anywhere near the HackRF. I don't recall the exact spec, but >> basically if you transmit with a 5 Watt HT, right next to HackRF, you can >> fry the RF front end. >> >> >> >> Hope that helps. >> >> Jake >> >> >> ------------------------------ >> >> *From:* HackRF-dev <hackrf-dev-boun...@greatscottgadgets.com> on behalf >> of Jerry Stern <jster...@att.net> >> *Sent:* July 10, 2017 2:54:16 PM >> *To:* hackrf-dev@greatscottgadgets.com >> *Subject:* [Hackrf-dev] Is my new (old) HackRF Deaf? >> >> >> >> Is my HackRF deaf? I am a ham radio hobbyist and I bought a HackRF One >> to enhance my deeper learning of SDR but also as a broadband RF source. To >> my dismay, installing the software has become days of learning Ubuntu >> basics and dealing with instructions that are at times outdated or nuanced >> towards a person with much more than basic Linux skills. So, I gave up on >> Ubuntu only because it was faster for me to install and test with Windows >> 7. My HackRF One (GreatScott) must have been a leftover as the firmware >> was dated 2014(August). I installed the latest version HackRF tools and >> updated the firmware to Feb 2017. I followed Mike's video tutorial for >> creating a basic GNU flow for FM and also installed SDR#. I have very >> strong FM broadcast stations in my area which I can easily demodulate with >> my Rigol Spectrum analyzer using the ANT500. However both with GNU and SDR# >> my HackRF appears deaf in FM broadcast mode. I read that a few years back >> there may have been some issues with cold solder joints on the HackRF >> pcb.... I have a lot of test equipment - from RF generators up to 2 GHz, >> etc but before I go that route is there something I am perhaps missing in >> my setup. Not sure where or what details to provide here without >> overloading my question further . >> >> >> >> Thanks >> >> >> >> Jerry >> >> >> >> >> Sent from my iPhone >> >> _______________________________________________ >> HackRF-dev mailing list >> HackRF-dev@greatscottgadgets.com >> https://pairlist9.pair.net/mailman/listinfo/hackrf-dev >> >>
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