# Fwd: Problem with getting clear FM signals using the usrp e110 **URL:** \ **Category:** GNU Radio\ **Created:** [April 9, 2014, 1:42pm UTC](https://www.ruby-forum.com/t/fwd-problem-with-getting-clear-fm-signals-using-the-usrp-e110/240356 "2014-04-09T13:42:41Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [April 9, 2014, 1:42pm UTC](https://www.ruby-forum.com/t/fwd-problem-with-getting-clear-fm-signals-using-the-usrp-e110/240356/1 "2014-04-09T13:42:41Z")
Here are some pointers for you: - Firstly, your screenshot shows the error message saying that the RX frequency is not valid. I’d recommend using a WBX daughterboard, however the BasicRX should still work with strong FM signals with aliasing if that is what you are using. - The samp\_rate is set to 100e3. It should be the master clock rate of the e110 divided by an even number such as 64e6/256 (250e3). - The quadrature rate in the WBFM receive block should be set to samp\_rate (250e3) and the Audio decimation should be set to 5. - The audio sink sample rate should be set to samp\_rate/audio\_decim (250e3/5=50e3). 50e3 is as close to the wanted audio sample rate of 48e3 that you are going to get without using one of the resampler blocks. Mike – Mike J. M0MIK BSc MIET Email: removed\_email\_address@domain.invalid Web: [http://scanoo.com](http://scanoo.com) ---------- Forwarded message ---------- From: Abouda Y. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Date: Wed, Apr 9, 2014 at 12:09 PM Subject: Re: [Discuss-gnuradio] Problem with getting clear FM signals using the usrp e110 To: Mike J. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) hi Mike, thx for offering help.I enclosed both a picture of the fm receiver and the grc file(because i’m using the embedded gnuradio version on the usrpe 110),so it might not open correctly to you.I will be waiting for your answer. 2014-04-09 11:47 GMT+02:00 Mike J. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): Abouda, ---
**Author:** ![cobra050](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/3d9bf3/32.png) [@cobra050](https://www.ruby-forum.com/u/cobra050)\ **Post date:** [April 9, 2014, 2:58pm UTC](https://www.ruby-forum.com/t/fwd-problem-with-getting-clear-fm-signals-using-the-usrp-e110/240356/2 "2014-04-09T14:58:02Z")
First 100k is insufficient sample rate from the E110. An FM station has 150 kHz total swing (+/- 75 kHz) so the frequency range of your E110 complex output is 100 kHz and is therefore insufficient for the entire modulation. You then feed the 100k sample per second signal into the FM block where you have informed it you will be sending 500 kHz (quadrature rate) and then with no decimation at all, you send the 500 kHz sample rate detected audio to a sound block where you’ve told it to expect 96 kHz audio. [image: \left [ 0.9 \left [ \frac{A+B}{2} + \frac{A-B}{2}\sin4\pi f\_pt \right ] + 0.1\sin2\pi f\_pt \right ] \times 75~\mathrm{kHz}] is the instantaneous frequency of an FM stereo broadcast signal where A is the left channel, B is the right channel and fp is the pilot tone frequency (19 kHz). Consider matching sample rates between these blocks as the software defined radio equivalent of “impedance matching” between analog circuits in one view of it. Bob ---
**Author:** ![cobra050](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/3d9bf3/32.png) [@cobra050](https://www.ruby-forum.com/u/cobra050)\ **Post date:** [April 10, 2014, 12:28pm UTC](https://www.ruby-forum.com/t/fwd-problem-with-getting-clear-fm-signals-using-the-usrp-e110/240356/3 "2014-04-10T12:28:27Z")
Thank you all for your responses.I tried to follow your instructions and I did a lot of experiments to make the fm\_receiver work.I have come to some conclusions,the USRP E110 is really not that powerful,I frankly say that I am disappointed.According to my personal experiments the maximum sample rate for the fm\_receiver was 1M and I matched between the different blocks to get a clear sound at the end.But,when I move the mouse the sound gets interrupted until I stop moving and when I add an FFT sink it makes it worse.So, I believe that I reached here the limits of the RAM ressources I think,and this proves that the USRP E110 is not powerful or maybe not dedicated for these applications(I am using the BASIC RX and TX daughterboards).Plz do not hesitate to correct me if I was misjudging the device because I am a newbie here !! Yassine 2014-04-09 14:55 GMT+02:00 Robert McGwier [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): ---
**Author:** ![cobra050](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/3d9bf3/32.png) [@cobra050](https://www.ruby-forum.com/u/cobra050)\ **Post date:** [April 10, 2014, 12:48pm UTC](https://www.ruby-forum.com/t/fwd-problem-with-getting-clear-fm-signals-using-the-usrp-e110/240356/4 "2014-04-10T12:48:19Z")
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi Yassine, Please don’t be disappointed. Honestly, it’s a little unfair: You demand graphical + signal processing performance from an embedded device. People often do this, and I usually like to explain the following: This embedded device has, for the ease of use, a graphical interface. This doesn’t make it a substitute for a PC. It is not a weak PC. If you wanted that, you would have bought an old PC and a b100. It is a powerful embedded device. It’s intended purpose is of course a demonstration of capabilities (like showing the spectrum of a signal), but foremost it is meant to be used as a remote device doing its signal processing on its own, without a user sitting in front of it. Example? You wouldn’t want to install a PC with a screen at every GSM tower. You’d like to have a small box with a network interface that you can access remotely to install your new signal processing routines. It is nice if it has a screen port so a technician might check stuff when he’s at the tower. However, that’s not the main feature of that box. So basically, you’re asking a lot for a device that uses a small wall wart as power supply – it’s not a substitute for a signal processing workstation but a device where you can test and deploy the algorithms you develop on a PC comfortably. Greetings, Marcus On 10.04.2014 12:27, Abouda Y. wrote: > powerful or maybe not dedicated for these applications(I am using > > > range of your E110 complex output is 100 kHz and is therefore > > > > > the RX frequency is not valid. I’d recommend using a WBX > > > > > > > > the quality of the sound is very bad it’s like on the SAW > > > > Amateur Radio Assn. (K4KDJ) > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Discuss-gnuradio > mailing list [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - [http://www.enigmail.net/](http://www.enigmail.net/) iQEcBAEBAgAGBQJTRnaVAAoJEBQ6EdjyzlHt4DcH/0EDizevAJ7HAhsXVStiLSe+ 1tTZ9/NxqkSfDJwZNp5AVWiETy5AzRG4DSrSsW1zTpV+QWfz1eHaK/H6vUbeGzxe 8BVonYhOKq8Z83i5jcrc7UyGEexszuiCN4hjRtO7ySQ3bHBa9pteu1nrOgaaOq3I U1ONjRP+gv6/rOyTUgIOgextUgnm4h6UE0VBmMc0b9nXKV5hvnExXirawwOeijFp oUakF6e1qP/43a4s/iIzB1VBN6SUvdBM8X3pLiXIT16sSY+etBXd18k/iopPm5Z5 HT55BnNCrUOxPYhNQGIKNKUY/yR5FPqJI4KbIDGanHtoTlDd2wNjIWzWGD3f8hg= =HbNz -----END PGP SIGNATURE----- ---
**Author:** ![cobra050](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/3d9bf3/32.png) [@cobra050](https://www.ruby-forum.com/u/cobra050)\ **Post date:** [April 10, 2014, 4:02pm UTC](https://www.ruby-forum.com/t/fwd-problem-with-getting-clear-fm-signals-using-the-usrp-e110/240356/5 "2014-04-10T16:02:48Z")
On 04/10/2014 06:27 AM, Abouda Y. wrote: > proves that the USRP E110 is not powerful or maybe not dedicated for > these applications(I am using the BASIC RX and TX daughterboards).Plz > do not hesitate to correct me if I was misjudging the device because I > am a newbie here !! > > Yassine The E1xx series are NOT “a PC in a wierd box”. They’re embedded platforms for embedded applications involving SDR. The on-board CPU isn’t in the same league as most desktop multi-core processors, and even though it runs an embedded Linux, it’s not just a “tiny desktop machine”. The intended use for these platforms has always been that heavy-lifting signal processing would happen on the FPGA, so most users of this platform are adept at implementing algorithms on the FPGA, with the CPU largely acting in a “supervisory” role. Now, it turns out that there are some applications where most of the signal processing will “fit” on the embedded CPU. There are ports, for example, of OpenBTS to the E1xx series. But asking it to do signal processing _and_ GUI user-interface work at the same time is asking a _lot_ of that single-core ARM CPU.