On 04/10/2014 06:27 AM, 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
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.
2014-04-09 14:55 GMT+02:00 Robert McGwier <rwmcgw...@gmail.com
<mailto:rwmcgw...@gmail.com>>:
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.
\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 <m...@scanoo.com
<mailto:m...@scanoo.com>> 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: m...@scanoo.com <mailto:m...@scanoo.com>
Web: http://scanoo.com
---------- Forwarded message ----------
From: *Abouda Yassine* <abouda21yass...@gmail.com
<mailto:abouda21yass...@gmail.com>>
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 <m...@scanoo.com <mailto:m...@scanoo.com>>
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 <m...@scanoo.com
<mailto:m...@scanoo.com>>:
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: m...@scanoo.com <mailto:m...@scanoo.com>
Web: http://scanoo.com
On Tue, Apr 8, 2014 at 12:18 PM, Abouda Yassine
<abouda21yass...@gmail.com
<mailto:abouda21yass...@gmail.com>> 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
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--
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)
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