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hello this is John moles burry with Edison research we're creating this video to give a brief and simple example of how to use the universal software radio peripheral or USRP with a new radio now this is going to radio companion or GRC and it's a graphical environment that can be used to create a new radio flow graphs if you're not familiar with ginyu radio or the u.s. RP feel free to follow the links below this video to find more information now today we're actually just going to build a FM receiver and show how simple it is to create software radios so to get started we need to go get a UHD USRP device or USRP block and what this does is it allows you to access the samples from the USRP and configure it accordingly so there's a number of parameters that can be set here for our first example we're not going to get getting into all of them but we'll definitely show them at some point in other videos the ones that are critical for each application usually are the orange ones for example sample rate is what sets the baseband sample rate that you get from the USRP after decimation and that can be set anywhere from 250 kilohertz to 25 megahertz when you're running in 16-bit mode with the USRP and 200 or and 210 now for this case it is controlled by a variable which I'll sit here momentarily 2 5 megahertz we're also going to have a graphical based variable to control the frequency which I'll add shortly and I could add a variable for the gain as well but to make it simple I'll just hard code the value and the same thing for the antenna now and using a WB x daughterboard with the end 200 and it has two ports are X 2 and tx/rx so I'll just select it to be arcs 2 of course that's what's actually connected to the antenna outside now as I mentioned this is going to be 5 megahertz for the sample rates so we'll set that in here and I do need to add the variable for the frequency which I move over here and we're just gonna call it freak just like we did in the UHD source and I'll set it to a default value of 105.7 megahertz which is a vowel channel for FM now we're getting started we'll go ahead and save the example before we lose any progress and we'll continue building the flow graph now for visualization I'm going to include a WX QE FFT and this will show us the contents of the RF spectrum and will help us you know tune the stations accordingly so some things to add here baseband frequency I'm going to set it to a value freak so all the values shown on the FFT are relative to the frequency that we've set instead of zero Hertz also I'm going to add what's called a notebook feature which will add some tabs that'll make the application look a little bit neater and I'll add that component a little bit later next we're going to add a channel filter which is simply a low-pass complex filter in this particular application remember that this is operating on both the I and Q so it's like there's actually two filters here each operating on a floating-point number or floating-point stream so we'll set the half bandwidth of the desired channel bandwidth here as well as the transition with now the transition with determines how many taps the filter will use and how quickly the filter rolls off will also set this filter to perform decimation so that the entire flow graph does not need to operate at five megahertz because that's not necessary for the bandwidth of an FM signal so we'll connect the source to the low-pass filter and next we're gonna add a wideband FM receiver WB FM for short okay and inside here the parameters are the quadrature rates which is going to be the output rate of this low-pass filter five megahertz divided by 20 is 250 kilohertz and I'll actually set the audio decimation for one so there will be no decimation across this particular block instead I'm going to use a rational resampler and the purpose of this is to take the sample rate which is a factor of the US RP master clock of a hundred megahertz and instead set it to what the sound card can operate at so I'll connect this to keep it simple we'll say will decimate by 250 and interpolate by 96 this can be reduced further but this is just a simple illustration this effectively changes the sample rate to 96 kilohertz which is what will set the sound card to so a sync is something where samples go into and we'll use an audio sync and this will actually route the samples to the sound card at the rate that we set here which will set the sound car to operate at 96 kilohertz the device name blank and it will select the default device of your operating system so I can go ahead and splice the demodulated audio into this desktop recording go ahead and create a WAV file sync as well and call this FM record sample rates gonna be 96 kilohertz like the audio sync and last but not least we'll add another FFT so we can actually look at the spectrum of the demodulated audio so we can see the composite signals so we can get a wider bandwidth view of the composite signal I'm actually going to set it to 250 kilohertz which is the output of the wideband FM receiver and we'll also assign this to a notebook tab okay now I'd still need to add the notebook so we'll go ahead and do that and what this is again is just a graphical feature that'll add tabs and make it a little easier to navigate the program will have one tab called our spectrum and another tab for a diamond spectrum try to take this correctly and at the moment I don't have any plans for a third tab so I'll get rid of that now once we're done designing our new radio flow graph in GRC we can actually use it to generate the Python file which is actually what your new radio executes with so let's change this ID so the file name is set appropriately and just give a quick check for any other things that might be missing doesn't look like there's any errors otherwise we would see red so we'll go ahead and generate the flow graph and we see that no errors have been produced and it's generated fm example dot PI and I'll go ahead and execute the photograph okay and it seems to be working I'll turn a verging on to help clarified its display a little bit you can see a number of broadcast FM stations in the spectrum here and we can go ahead and change the frequency that we're looking at something lower say 95 megahertz there's additional stations let's go back to some of the clean ones that we saw here so again this is the RF spectrum you can clearly hear that we're listening to a signal that's being demodulated by this block here and of course filtered and resample etc it's also helpful to go ahead and look at the daemon spectrum so you can see some of the contents of the FM composite signal so here you have the mono signal a pilot tone that that gives you a reference for the first subcarrier here this is the rdsing let's use to transfer a digital information like the name of the song and then there's some other functions in this spectrum as well that's a pretty quick example of how to use the USRP with GRC and it shows that things are pretty flexible in this graphical environment allows you to create things pretty quickly if you have any questions feel free to contact us at support at editcom and again if you're unfamiliar with any of this feel free to look at some of the links below this video thank you for your time and I look forward to showing you more examples with the u.s. RP