Re: [Discuss-gnuradio] Fwd: Problem with getting clear FM signals using the usrp e110

[Marcus Müller]

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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 Yassine wrote:
> 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 <address@hidden>:
> 
>> 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
>> 
>> 
>> 
>> 
>> 
>> On Wed, Apr 9, 2014 at 7:40 AM, Mike Jameson <address@hidden>
>> wrote:
>> 
>>> 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 Jameson M0MIK BSc MIET Email: address@hidden Web:
>>> http://scanoo.com
>>> 
>>> 
>>> ---------- Forwarded message ---------- From: Abouda Yassine
>>> <address@hidden> 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 Jameson <address@hidden>
>>> 
>>> 
>>> 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 Jameson <address@hidden>:
>>> 
>>> Abouda,
>>>> 
>>>> If you attach your GRC file to your reply I'll take a look at
>>>> it for you.  It sounds like a sample rate mis-match going on
>>>> somewhere.
>>>> 
>>>> Mike
>>>> 
>>>> -- Mike Jameson M0MIK BSc MIET Email: address@hidden Web:
>>>> http://scanoo.com
>>>> 
>>>> 
>>>> On Tue, Apr 8, 2014 at 12:18 PM, Abouda Yassine < 
>>>> address@hidden> wrote:
>>>> 
>>>>> Hello, I followed this tutorial to build a simple FM
>>>>> receiver: https://www.youtube.com/watch?v=KWeY2yqwVA0.I am
>>>>> using the USRP e110,my problem is I am only getting noise.I
>>>>> tried to change blocks and parameters and it worked for me
>>>>> when I deleted the rational resampler and made a 100k as a
>>>>> sample_rate parameter.I get to hear FM radio stations but 
>>>>> the quality of the sound is very bad it's like on the SAW
>>>>> movie.Any one has a solution on how to improve the sound
>>>>> quality!!!!thx
>>>>> 
>>>>> _______________________________________________ 
>>>>> Discuss-gnuradio mailing list address@hidden 
>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>>> 
>>>>> 
>>>> 
>>> 
>>> 
>>> _______________________________________________ 
>>> Discuss-gnuradio mailing list address@hidden 
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>> 
>>> 
>> 
>> 
>> -- Bob McGwier Co-Owner and Technical Director, Federated
>> Wireless, LLC Professor Virginia Tech Senior Member IEEE,
>> Facebook: N4HYBob, ARS: N4HY Faculty Advisor Virginia Tech
>> Amateur Radio Assn. (K4KDJ)
>> 
> 
> 
> 
> _______________________________________________ Discuss-gnuradio
> mailing list address@hidden 
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
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