Re: [USRP-users] USRP E313 | WBFM Issues

[Marcus Müller via USRP-users]

Hi Ryan,

hm, there's honestly quite a few things that can simply go wrong on a
demodulation/DSP/signal side of things without nothing misbehaving or
you doing any mistakes. Your single-tone test hence was very clever to
do!

So, my recommendation is this:
First of all, verify that the reception strength / SNR is actually
reasonably good. You said you saw the signal in a frequency plot – so
how many dB were between signal and noise floor? If it's worse than
let's say 20 dB, you might need more RX gain or a better antenna (FM in
cities typically is pretty strong).

If that is fine, *make a raw recording* (using either GNU Radio with a
file sink directly attached through a head block to the USRP source, or
with the rx_samples_to_file tool) of a few seconds worth of samples,
and try to demodulate them on your PC – if that doesn't work, we know
there's something else to fix.

Best regards,
Marcus
  
On Fri, 2018-09-21 at 15:28 -0400, Ryan Campiz via USRP-users wrote:
> 
> Ryan Campiz  
> Thu, Sep 20, 5:21 PM (21 hours ago)
> 
> to support 
> Greetings,
> 
> I'm having trouble with a basic Wide-Band FM (WBFM) demodulation
> tutorial. I am using the Ettus USRP E313. The Ettus USRP E313 is
> basically an enclosure with an Ettus E310 and Power/Ethernet PCB with
> the RF, DC Power, Ethernet, and USB ports.
> 
> FM DEMODULATION TUTORIAL
> In my application, as the host machine, I am using a Virtual Machine
> with Ubuntu 16.04 (64-bit). I downloaded all of the software as
> instructed in the AN-445 Ettus Application Note.
> 
> In my application, the tutorial that I am following is from the AN-
> 335 Application Note from Ettus. The tutorial is not complicated. I
> downloaded the Flowgraph files that the tutorial comes with. When I
> generate both python files and run them respectively on the E310 and
> the Host Machine, all I hear is static. I can see evidence of a
> received signal on the Frequency Spectrum graph, but I only hear
> static. What’s more, as I vary the radio frequency, I do see the
> Frequency Spectrum graph change, but I see no evidence of any FM
> Radio Stations.
> 
> DETOUR: DEMONSTRATING I COULD AT LEAST HEAR A 1KHZ TONE FROM THE E310
> Just to make sure that it was possible to hear anything from the
> E310, I created a simple flowgraph for the E310. All it did was
> generate a Signal Source: a tone of 1kHz. On the other end, with the
> VM, I had an Audio Sink and a Time Graph and Waterfall Diagram. I was
> able to hear the tune. But it was choppy. And there was latency with
> the controls. A system block diagram of this set-up can be seen
> below. 
> 
> 
> LAST EFFORTS AND SPECULATION
> After demonstrating that I could hear at least a tone, I moved back
> to the FM Demodulation Tutorial. I tried for a day to get it to run.
> After no success, I used other resources to try to find where the
> process could be going wrong. Once such resource is the YouTube video
> "How To Build an FM Receiver with the USRP in Less Than 10 Minutes".
> That YouTube video is made by Ettus Research.  It was well-produced
> and easy to follow. However, even after watching it several times I
> could not locate what could be going wrong in the RF Demodulation
> flowgraph.
> 
> I am so uncertain at this point that I am starting to wonder if
> either:
> 
> A.  the RF Front End is not working, or
> B.  the OS image on the Ettus E310 is very slightly corrupted, or
> C.  the FPGA is not programmed (built?) correctly.
> 
> What could be going wrong?
> 
> 
> 
> 
> 
> Ryan Campiz
> Electrical/RF Engineer
> AREA-I
> where ideas take flight
> 
> 1590 N. Roberts Rd., Ste 102
> Kennesaw, GA 30144
> 1590 N. Roberts Rd., Ste 102
> Kennesaw, GA 30144
> Direct: 470-481-4054
> Fax: 678-594-5228
> 
> PROPRIETARY AND CONFIDENTIAL: This message, including any attachment,
> is confidential information of Area-I, Inc. This message may contain
> information that is privileged and exempt from disclosure under
> applicable law and is intended only for the individual or entity to
> which it is addressed. If the reader of this message is not the
> intended recipient, or the employee or agent responsible for
> delivering the message to the intended recipient, you are notified
> that any use, dissemination, distribution or copying of this
> communication is strictly prohibited. If you have received this
> communication in error, please contact the sender immediately by e-
> mail and destroy all copies of the original message and any
> attachment.
> INTERNATIONAL TRAFFIC IN ARMS REGULATIONS (ITAR) NOTICE: Any
> drawings, specifications, or other proprietary data contained within,
> or associated with this correspondence, or any subsequent
> correspondence including, but not limited to U.S. Post, faxes, etc.,
> are considered controlled data. As such, this data/information is
> subject to U.S. Export Control under the Department of State,
> International Traffic in Arms Regulation (ITAR). These
> drawings/specifications may not be exported o

[USRP-users] USRP E313 | WBFM Issues

[Ryan Campiz via USRP-users]

Ryan Campiz 
Thu, Sep 20, 5:21 PM (21 hours ago)
to support

Greetings,

I'm having trouble with a basic Wide-Band FM (WBFM) demodulation tutorial.
I am using the Ettus USRP E313. The Ettus USRP E313 is basically an
enclosure with an Ettus E310 and Power/Ethernet PCB with the RF, DC Power,
Ethernet, and USB ports.
FM DEMODULATION TUTORIAL

In my application, as the host machine, I am using a Virtual Machine with
Ubuntu 16.04 (64-bit). I downloaded all of the software as instructed in
the AN-445 Ettus Application Note.

In my application, the tutorial that I am following is from the AN-335
Application Note from Ettus. The tutorial is not complicated. I downloaded
the Flowgraph files that the tutorial comes with. When I generate both
python files and run them respectively on the E310 and the Host Machine,
all I hear is static. I can see evidence of a received signal on the
Frequency Spectrum graph, but I only hear static. What’s more, as I vary
the radio frequency, I do see the Frequency Spectrum graph change, but I
see no evidence of any FM Radio Stations.
DETOUR: DEMONSTRATING I COULD AT LEAST HEAR A 1KHZ TONE FROM THE E310

Just to make sure that it was possible to hear anything from the E310, I
created a simple flowgraph for the E310. All it did was generate a Signal
Source: a tone of 1kHz. On the other end, with the VM, I had an Audio Sink
and a Time Graph and Waterfall Diagram. I was able to hear the tune. But it
was choppy. And there was latency with the controls. A system block diagram
of this set-up can be seen below.
[image: image.png]
LAST EFFORTS AND SPECULATION

After demonstrating that I could hear at least a tone, I moved back to the
FM Demodulation Tutorial. I tried for a day to get it to run. After no
success, I used other resources to try to find where the process could be
going wrong. Once such resource is the YouTube video "How To Build an FM
Receiver with the USRP in Less Than 10 Minutes". That YouTube video is made
by Ettus Research.  It was well-produced and easy to follow. However, even
after watching it several times I could not locate what could be going
wrong in the RF Demodulation flowgraph.

I am so uncertain at this point that I am starting to wonder if either:

A.  the RF Front End is not working, or

B.  the OS image on the Ettus E310 is very slightly corrupted, or

C.  the FPGA is not programmed (built?) correctly.

What could be going wrong?




*Ryan Campiz*
Electrical/RF Engineer
AREA-I
*where ideas take flight*

*1590 N. Roberts Rd., Ste 102*
*Kennesaw, GA 30144*
1590 N. Roberts Rd., Ste 102

Kennesaw, GA 30144

Direct: 470-481-4054
Fax: 678-594-5228

PROPRIETARY AND CONFIDENTIAL: This message, including any attachment, is
confidential information of Area-I, Inc. This message may contain
information that is privileged and exempt from disclosure under applicable
law and is intended only for the individual or entity to which it is
addressed. If the reader of this message is not the intended recipient, or
the employee or agent responsible for delivering the message to the
intended recipient, you are notified that any use, dissemination,
distribution or copying of this communication is strictly prohibited. If
you have received this communication in error, please contact the sender
immediately by e-mail and destroy all copies of the original message and
any attachment.
INTERNATIONAL TRAFFIC IN ARMS REGULATIONS (ITAR) NOTICE: Any drawings,
specifications, or other proprietary data contained within, or associated
with this correspondence, or any subsequent correspondence including, but
not limited to U.S. Post, faxes, etc., are considered controlled data. As
such, this data/information is subject to U.S. Export Control under the
Department of State, International Traffic in Arms Regulation (ITAR). These
drawings/specifications may not be exported or re-exported without written
authorization and a valid U.S. export license.
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