Fwd: Problem with getting clear FM signals using the usrp e110

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: [email protected]
Web: http://scanoo.com

---------- Forwarded message ----------
From: Abouda Y. [email protected]
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. [email protected]

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. [email protected]:

Abouda,

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

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 [email protected]:

-----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 [email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Thunderbird - 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-----

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.

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs