problems with rtl_sdr on Fedora 23

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davephillips
Posts: 2
Joined: Sat Jan 20, 2018 8:54 pm

problems with rtl_sdr on Fedora 23

Post by davephillips » Sat Jan 20, 2018 9:59 pm

Greetings ! I'm a new user of the rtl_sdr dongle, just got my kit today (RTL-SDR Blog R820T2 RTL2832U 1PPM TCXO SMA Software Defined Radio with 2x Telescopic Antennas). I get the following report from 'rtl_test -t' :

$ rtl_test -t
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
Sampling at 2048000 S/s.
No E4000 tuner found, aborting.

Looking good so far, but when I try using gqrx I get no signal at all, regardless of settings. I launch the program at the prompt, where I receive a series of the following errors when I adjust the frequency values :

r82xx_write: i2c wr failed=-4 reg=17 len=1
r82xx_set_freq: failed=-4
rtlsdr_demod_write_reg failed with -4
rtlsdr_demod_read_reg failed with -4
rtlsdr_demod_write_reg failed with -4
rtlsdr_demod_read_reg failed with -4

Both gqrx and the rtl_sdr suite have been installed from the Fedora 23 repos.

As far as I can tell, I have gqrx configured correctly, but as I say, I'm a complete newbie to this stuff. I am however a long-time user of Linux (20+ years), I can and do compile software routinely here, and I'm quite willing to try about anything to get this thing working. I've been through the quick-start guide but got no joy, so I'm turning to this forum for help. Any suggestions ? Please advise if more information is needed. (I checked through all 18 pages of the troubleshooting forum but haven't yet found any messages with the identical problem.)

Btw, I'm interested in sdr for a couple of reasons, the primary being its use in a virtual Eurorack setting called VCV Rack, it's a software modular synthesis environment that includes a module for use with rtl_sdr. The other reason is that I was a ham radio operator when I was a teenager, it was a lot of fun then and I'm curious about this software radio thing. :)

TIA for any & all assistance !

Dave Phillips

rtlsdrblog
Site Admin
Posts: 2699
Joined: Mon Nov 19, 2012 11:54 pm

Re: problems with rtl_sdr on Fedora 23

Post by rtlsdrblog » Sun Jan 21, 2018 6:10 am

rtl_test looks good, but try it without the -t flag. The -t flag is only for E4000 units.

Some people have reported that the rtlsdr_demod_write_reg failed with -4 error occurs when the USB port in use doesn't produce enough voltage. Can you try other USB ports, or maybe a powered USB hub too?

Do you have another PC you can try with?

Also try running rtl_fm http://kmkeen.com/rtl-demod-guide/. You can rule out a hardware fault if that works.

davephillips
Posts: 2
Joined: Sat Jan 20, 2018 8:54 pm

Re: problems with rtl_sdr on Fedora 23 [SOLVED]

Post by davephillips » Sun Jan 21, 2018 11:25 am

rtlsdrblog wrote:
Sun Jan 21, 2018 6:10 am
rtl_test looks good, but try it without the -t flag. The -t flag is only for E4000 units.

Some people have reported that the rtlsdr_demod_write_reg failed with -4 error occurs when the USB port in use doesn't produce enough voltage. Can you try other USB ports, or maybe a powered USB hub too?

Do you have another PC you can try with?

Also try running rtl_fm http://kmkeen.com/rtl-demod-guide/. You can rule out a hardware fault if that works.
Many thanks for your reply and suggestions, I now have a working system. The solution was the powered hub. I have an old Belkin 4-port hub that works perfectly with the dongle, and my tests are now producing audible results. Not very impressive results yet, but I've done no tuning at this point. The VCV Rack module now works "as advertised", which was my main goal, and I'm looking forward to doing some very strange things with it. :)

Btw, some information for reference :

mobo: Gigabyte GA-78LMT-USB3
CPU: AMD FX6300 6-core 3.5 GHz
memory: 16GB
system: Fedora 23 Linux, GCC 5.3.1

Thanks again !

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