Gqrx not receiving any signals with RTL-SDR Dongle

[Terry Osborne]

Hi,

I'm just getting started with Linux and I'm trying to use an Ezcap Dongle or an RTL-SDR v2 Dongle to receive new Amateur Radio Satellite AO-91.

I have a Toshiba A100 Laptop that I have installed with Lubuntu 16.04 from the Linux Format Magazine DVD.

I followed the steps for a Ubuntu install from the web page and it worked OK.

When I plug the Dongle in, Gqrx will find the Dongle and appears to work but will not receive any signals.

Spectrum display just shows a few pips.

The Dongle is not faulty because I checked it with SDR# on a Windows 7 box.

Any suggestions as to what may be missing ?

73,

Terry Osborne ZL2BAC

[Simon Kennedy]

Hi Terry,

Presumably you have pressed the 'play' button top left to start demodulation. Assuming so check the mode is set to something other than 'Demod off' but most importantly turn up the gain settings and/or tick the Hardware AGC option.

If this doesn't help start gqrx from the command line and post the output here along with a screenshot of the gqrx window.

HTH

Simon

G0FCU.

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[Wendy and Terry Osborne]

Hi Simon,

 

Thanks for the reply.

First off, If I select “Device > RTL-SDR Spectrum Server” then Gqrx and terminal crash.

“Device > Realtek RTL2838UHIDIR” then Gqrx runs OK. See Gqrx_Screenshot1.

But will not receive any signals (very low RF levels?). See Gqrx_Screenshot2.

On the Input controls page, I can’t select the “LNA gain”. Stuck at minimum.

I can select the tick boxes.

 

Also attached are the Terminal readouts.

You can see the terminal crashing at the end of the Gqrx_terminal file.

I have WFM (stereo) selected as the “Mode”

 

73,

 

Terry ZL2BAC

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[Robin Gape]

Terry,

1) I've attached the terminal output from a successful GQRX invocation with an RTL Dongle, in this case a NooElec SDR Smart dongle.

2) Comparing by eye (or using diff or a GUI diff if one prefers) the key difference is in the line from your transcript:

Using device #0 Realtek RTL2838UHIDIR
Detached kernel driver
No supported tuner found
Enabled direct sampling mode, input 1

What this implies is that either GQRX can not see the dongle, or that the dongle's tuner chip is not supported.

3) Since you are using an Ubuntu 16.04 variant, then, when you installed GQRX, no further configuration should be necessary. [A udev rule is included in librtlsdr0, and includes extensive options to capture many known devices.]

4) Do you get the same results with both dongles? It is possible to get dongles which are not supported under Linux, but which will perform under Windows. [Generally due to a chip manufacturer's unwillingness to disclose necessary interface information, except under an Open Source incompatible NDA.]

4A) Do you get the same results on all USB2 ports? [Sometimes chip manufacturers feel that lawyers are cheaper than competent logic designers!]

5) To diagnose further, what are the results of lsusb with each of the dongles? lsusb requires the installation of package usbutils.

5A) A further diagnosis is to install package rtl-sdr, and then to run rtl_test. What results do you get from each of the dongles?

6) A great deal of stuff on the general Internet on the use of RTL dongles under Linux is very out-of-date. This compatibility list was last revised 2 years ago, but may be helpful: https://www.reddit.com/r/RTLSDR/wiki/compatibility.

Good luck, and hopefully you'll get there,

Robin, G8DQX

[Simon Kennedy]

Terry,

my RTL dongle is showing as the same device as yours. As Robin has pointed out your terminal output is different. I've attached my output for information.

Otherwise follow Robin's fault finding steps.

I did a complete fresh install of gqrx and only ended up with 2.6.1 rather than 2.9 (on xubuntu 16.10) but I doubt that will make a difference.

Regards

Simon.

[Alexandru Csete]

For some reason I can not see the attachments in this thread. They all
appear as binary files of unknown type. Anybody else experience this?

Alex

[Wendy and Terry Osborne]

Hi Alex and team,

That's my fault.
I'm new to using the screen capture and leafpad.
When I saved the files, I didn't add an extension.
So here the are again.

Thanks,
Terry Osborne

-----Original Message-----
From: Alexandru Csete
Sent: Thursday, January 04, 2018 9:09 AM
To: gq...@googlegroups.com
Subject: Re: [gqrx] Gqrx not receiving any signals with RTL-SDR Dongle

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[Alexandru Csete]

I can see in the console output that:

> No supported tuner found

and consequently:

> Gain name: "LNA"
> min: 0
> max: 0
> step: 0

So, for some reason the driver can not find the tuner part of the
dongle (RF frontend), only the digital part. I don't know how this can
happen with a healthy sdr dongle.

Does rtl_test work?

Alex

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[Robin Gape]

Alex,

it can happen because there are two chips in an RTL 2832U dongle. For whatever reasons, not all tuner chips are supported by Linux, probably due to nasty NDAs. That was the point of the compatibility list link in my earlier post.

So a dongle can be fine under Windows with a closed-source driver. But under Linux, no open source driver is possible, due to NDA restrictions.

So, sadly, it's caveat emptor,

73,

Robin, G8DQX (burning midnight oil on a different project!)

[Wendy and Terry Osborne]

Hi Alex and Team,

I think I've found the problem.
Gqrx 2.9 doesn't support the old Tuner chip in the Ezcap EZTV646 dongle
(FC0012).
It works fine with the RTL-SDR v2 Dongle.
See attached terminal output from each Dongle.

Thanks for the help.

https://groups.google.com/d/msgid/gqrx/CAHG%3DS_ek8x2D3GU3tR41OQhoMmnAB_tJNCUS7ZHrh%2B5_%3DeRPDQ%40mail.gmail.com.

[Miguel Descalzo]

Hi,

I'm having the exact same problem, but with a a RTL-SDR_V3 and the GQRX 2.11.5.

Does someone knows if it can be fixed?

[Robin Gape]

Miguel,

1) the most likely cause of problems with an RTL-SDR V3 dongle is a lack of udev rule, though it could be something else. Did you install package rtl-sdr?

If not, then (assuming that you're using Ubuntu) install rtl-sdr using Synaptic, the software store or the terminal: apt-get install rtl-sdr. That automatically installs everything that the hardware should need.

2) to help you any further, you need to tell the rest of us what hardware you are using, how GQRX was installed, did you try different installation methods, what aerial is connected to the dongle, what frequency you're trying to receive, the OS and its version &c. &c. Without that information, we are shooting in the dark and unlikely to get to the real cause.

Robin, G8DQX

--

[Miguel Descalzo]

Ye... sorry for the lack of information.

rtl-sdr package is installed.

I'm using Ubuntu 16.04. GQRX was installed via the PPA and I haven't try other methods of installation. I have the same problem with any frequency I try to recive.

What exactly you want to know about the hardware I'm using? I don't know what to tell you about it.

Connected to the dongle I have a dipole antena.

I attach the output of the console when  GQRX is started and the output of a rtl_test -t.

I don't know if its enough information...

Thanks for your help 

[Robin Gape]

Miguel,

1) what rtl_test is saying is that, irrespective of the -t parameter, no tuner has been found that rtl-sdr is capable of supporting.

With a supported tuner (in this case with an R820T2 tuner chip), the output of rtl_test should be something like:

:~$ rtl_test
Found 1 device(s):
  0:  Realtek, RTL2838UHIDIR, SN: 00000001

Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Supported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
[R82XX] PLL not locked!
Sampling at 2048000 S/s.

Info: This tool will continuously read from the device, and report if
samples get lost. If you observe no further output, everything is fine.

Reading samples in async mode...
^CSignal caught, exiting!

User cancel, exiting...
Samples per million lost (minimum): 0

2) It looks as if the dongle hardware is not what you think that it is, or has failed in some way. Could you post what the last 6 lines of dmesg are, just after you installed the dongle, something similar to:

:~$ dmesg |tail -6
[833227.648177] usb 3-2: new high-speed USB device number 19 using xhci_hcd
[833227.843804] usb 3-2: New USB device found, idVendor=0bda, idProduct=2838
[833227.843807] usb 3-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[833227.843809] usb 3-2: Product: RTL2838UHIDIR
[833227.843811] usb 3-2: Manufacturer: Realtek
[833227.843812] usb 3-2: SerialNumber: 00000001

3) The transcript from the terminal is showing the same thing, that there is no recognised tuner:

Loading configuration from: "default.conf"
Configuration file: "/home/mdescape/.config/gqrx/default.conf"
gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.10
built-in source types: file osmosdr fcd rtl rtl_tcp uhd plutosdr miri hackrf bladerf rfspace airspy airspyhf soapy redpitaya
Using device #0 Realtek RTL2838UHIDIR SN: 00000001
No supported tuner found

4) According to the information and dat asheet available at https://www.rtl-sdr.com/rtl-sdr-blog-v-3-dongles-user-guide/, the RTL-SDR V3 dongle uses an R820T2.

Robin, G8DQX

--

[Miguel Descalzo]

Ok Robin, here it is:

:~$ dmesg |tail -6

[  152.656316] usb 1-1: new high-speed USB device number 5 using xhci_hcd

[  152.810035] usb 1-1: New USB device found, idVendor=0bda, idProduct=2838

[  152.810040] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3

[  152.810044] usb 1-1: Product: RTL2838UHIDIR

[  152.810048] usb 1-1: Manufacturer: Realtek

[  152.810051] usb 1-1: SerialNumber: 00000001

[Miguel Descalzo]

So, no idea? :(

[Robin Gape]

Miguel,

unavoidably distracted! Given the symptoms described, which are:

a) the hardware seems to be recognised as a valid RTL-SDR dongle

b) the hardware fails rtl_test

Then a resolution by substitution would seem to be the way to go. Either:

c) try another RTL-SDR dongle in the same machine using rtl_test, or

d) try the current RTL-SDR dongle in another machine, preferably a Linux box

The fact that the tuner is not recognised as an R820 indicates that either it has failed or it is not a supported tuner, which implies that the dongle is not an RTL-SDR V3. The symptoms could also be consistent with a software problem. The tests in c) and d) above should help to resolve the issue.

If the tuner is not an R820 or R820T2, or other supported tuner, then the dongle may work in a Windows machine, using a proprietary driver. [That is due to a manufacturer's choice not to make the necessary information available except possibly under NDA.]

HTH,

Robin, G8DQX

[David Ranch]

According to https://osmocom.org/projects/rtl-sdr/wiki/Rtl-sdr , this specific USB device is supported by the gr-osmo system so it should work.

--David
KI6ZHD