That makes sense then. Thanks!
----------------------------- Jacob Knoles On Fri, Aug 25, 2017 at 10:03 AM, <mle...@ripnet.com> wrote: > An LO offset tunes the analog hardware to desired_freq+LO_offset, and then > digitally basebands the desired frequency. However, if the analog > bandwidth is narrow enough that the digital basebanding (DDC) doesn't have > any useful signal, then this will be the result. > > > > > > > > > On 2017-08-25 12:47, Jacob Knoles wrote: > > Thanks. > > I didn't expect the actual input to shift with the LO offset. > > ----------------------------- > Jacob Knoles > > > On Fri, Aug 25, 2017 at 9:08 AM, <mle...@ripnet.com> wrote: > >> That's probably because you set your bandwidth to be somewhat narrow, so >> with offset tuning, you were only seeing the deeply-filtered data. >> >> >> >> >> >> >> On 2017-08-25 11:23, Jacob Knoles wrote: >> >> I found my issue. When I set my center frequency to monitor I also >> provided a LO offset. The intention is to not have the LO included in the >> response. >> >> For some reason it seams this pulled the receive frequency with it. By >> removing the LO offset I am getting the data I expect to see. >> >> At this time I am not sure why this is happening? >> >> ----------------------------- >> Jacob Knoles >> >> >> On Fri, Aug 25, 2017 at 8:12 AM, Jacob Knoles <knole...@gmail.com> wrote: >> >>> The numbers coming out are essentially zero. Looking at the chart it >>> reads -1.3e-17. There are a lot of values that do come out exactly zero, as >>> they become -inf (or something like -370) after going through the log10 >>> mathematics. >>> >>> The signal I am inputting however is a simulated BT signal with the peak >>> at -40 dBm and modulated. At the one frequency I am monitoring it results >>> in a square wave. So I expect to see a distinct change in the output >>> numbers. >>> >>> ----------------------------- >>> Jacob Knoles >>> >>> >>> On Thu, Aug 24, 2017 at 6:15 PM, Marcus D. Leech via USRP-users < >>> usrp-users@lists.ettus.com> wrote: >>> >>>> On 08/24/2017 08:11 PM, Jacob Knoles via USRP-users wrote: >>>> >>>> Hello, >>>> >>>> I am trying to do a simple receive function that grabs data for 12 >>>> seconds, calculates the log10 power and then plots power vs time. >>>> >>>> I am using the GnuRadio C++ API and have done a prototype using >>>> GnuRadio Companion. I am also feeding in a dummy signal using a vector >>>> signal generator. >>>> >>>> While running the Companion code I get exactly the results I expect to >>>> get, as seen in this image: >>>> >>>> [image: Inline image 1] >>>> >>>> The top time plot is displaying each step of the calculation chain, Red >>>> is the real part of the complex number, green is the imaginary part and >>>> blue is the magnitude. >>>> >>>> The lower plot shows the power vs time trace that I am after for this >>>> test, the calculation being used is 20*Log10(mag) - 17. >>>> >>>> The offset was calculated by comparing a known signal on a spectrum >>>> analyzer. >>>> >>>> So now my issue. When I take this prototype and implement it in C++ >>>> (that is what my program is using) I do not get any results back at all. >>>> >>>> Here is the C++ resulting plot of the real complex values only: >>>> >>>> [image: Inline image 2] >>>> >>>> As can be seen all the values are essentially zero. >>>> >>>> Here is the code snippet that is handling the capture, it returns a >>>> std::vector<float> which is plotted elsewhere in the software. (I have >>>> confirmed that the plotting software is not the issue.) >>>> >>>> _rate = 5e6; >>>> //---------------------------------------------------------- >>>> ---------------------- >>>> //-- Make a top block >>>> //---------------------------------------------------------- >>>> ---------------------- >>>> auto tb = gr::make_top_block( "TraceCapture" ); >>>> >>>> //---------------------------------------------------------- >>>> ---------------------- >>>> //-- make the usrp >>>> //---------------------------------------------------------- >>>> ---------------------- >>>> auto stream_args = uhd::stream_args_t( "fc32", "sc16" ); >>>> stream_args.channels.push_back( 0 ); >>>> auto usrp_source = gr::uhd::usrp_source::make( >>>> uhd::device_addr_t( "" ), stream_args ); >>>> usrp_source->set_samp_rate( _rate ); >>>> usrp_source->set_center_freq( uhd::tune_request_t(carrier_freq, >>>> 10e6) ); >>>> usrp_source->set_gain( _gain_one ); >>>> usrp_source->set_bandwidth( 1e6 ); >>>> usrp_source->set_antenna( "RX2" ); >>>> >>>> //---------------------------------------------------------- >>>> ---------------------- >>>> //-- Make the necessary flowgraph blocks >>>> //---------------------------------------------------------- >>>> --------------------- >>>> auto complex_to_mag_sptr = gr::blocks::complex_to_mag::make( ); >>>> //auto nlog10_sptr = gr::blocks::nlog10_ff::make( 20, 1, -17.4 >>>> ); >>>> auto vector_sink_sptr = gr::blocks::vector_sink_f::make( ); >>>> auto complex_to_real_sptr = gr::blocks::complex_to_real::make( >>>> ); >>>> >>>> //---------------------------------------------------------- >>>> ---------------------- >>>> //-- Connect the flowgraph >>>> //---------------------------------------------------------- >>>> ---------------------- >>>> //tb->connect( complex_to_mag_sptr, 0, nlog10_sptr, 0 ); >>>> //tb->connect( nlog10_sptr, 0, vector_sink_sptr, 0 ); >>>> //tb->connect( complex_to_mag_sptr, 0, vector_sink_sptr, 0 ); >>>> tb->connect( complex_to_real_sptr, 0, vector_sink_sptr, 0 ); >>>> tb->connect( usrp_source, 0, complex_to_real_sptr, 0 ); >>>> >>>> tb->start( ); >>>> std::this_thread::sleep_for( std::chrono::milliseconds( >>>> static_cast<long long>( capture_time * 1000 ) ) ); >>>> >>>> tb->stop( ); >>>> tb->wait( ); >>>> >>>> return std::make_shared<std::vector<float>>( >>>> vector_sink_sptr->data( ) ); >>>> >>>> >>>> When I run the code on my B210 I get no errors, the RX2 led lights as >>>> expected, all the numbers get calculated as expected yet no matter what I >>>> have tried I am getting only zeros from the B210 >>>> >>>> Additionally I am working on Windows 10 with VS 2015. I have installed >>>> a binary version of GnuRadio. Here is the flowgraph in grc for reference >>>> as well. >>>> >>>> [image: Inline image 1] >>>> >>>> Any help will be greatly appreciated!! >>>> >>>> Thanks >>>> >>>> ----------------------------- >>>> Jacob Knoles >>>> >>>> >>>> _______________________________________________ >>>> USRP-users mailing >>>> listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>> >>>> Do you mean "essentially zero" or actually zero? There's a difference. >>>> >>>> >>>> >>>> _______________________________________________ >>>> USRP-users mailing list >>>> USRP-users@lists.ettus.com >>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>> >>>>
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