[SOLVED] How easy/hard is SDR on Linux?

sgosnell · 09-06-2015, 09:54 AM

ATC doesn't broadcast on FM, in case you didn't know. Aviation frequencies worldwide are VHF AM.

273 · 09-06-2015, 09:56 AM

Unfortunately I don't have another aerial to try and it would likely cost more than the device to buy one. Can you think of anything I can try which would be guaranteed to get some kind of signal. I'm thinking that setting the frequency to that of a local radio station should get me something other than static even if I've chosen the wrong mode and I'm guessing the right mode would be "WFM (stereo)". On starting the application I am seeing:

Code:

gr-osmosdr 0.1.4 (0.1.4) gnuradio 3.7.8
built-in source types: file osmosdr fcd rtl rtl_tcp uhd miri hackrf bladerf rfspace airspy 
Using device #0 Realtek RTL2838UHIDIR SN: 00000001
Found Rafael Micro R820T tuner
[R82XX] PLL not locked!
[R82XX] PLL not locked!
Could not resolve property : pattern10600
Could not resolve property : pattern10600
Could not resolve property : pattern10600
Could not resolve property : pattern10600
Could not resolve property : pattern10600
Could not resolve property : pattern10600

With the "Could not resolve property" error repeated a good many times before this block. They look to me like simple advisories rather than errors but am I wrong here?

273 · 09-06-2015, 09:57 AM

Quote:

Originally Posted by sgosnell

ATC doesn't broadcast on FM, in case you didn't know. Aviation frequencies worldwide are VHF AM.

Thanks, yes, I'd realised that -- see the above post using a local FM station for troubleshooting in case the frequencies I've found for ATC at my local airport are out of date.

tredegar · 09-06-2015, 10:15 AM

Quote:

Unfortunately I don't have another aerial to try

Fortunately you can make one very easily:

Take any piece of wire about 75cm long (1/4 wavelength of 100MHz (FM band in UK)).

Strip insulation from last 1-2cm. Poke this into the central bit (it's usually hollow) of the aerial socket on your dongle, bend the wire back on itself a couple of times if it is loose in the central connector. Do NOT short it to the circular, outer metal bit (that is for connecting to the braid round a CoAx cable). We don't need this.

Tune to a local FM station. Hope.

tredegar · 09-06-2015, 10:25 AM

....Also, some SDR implementations need you to "Start" the radio, once you have set the tuning, demodulation etc. Have you missed the "Start" or equivalent button?

As for "Could not resolve property : pattern10600" a search leads to this:

https://groups.google.com/forum/#!to...rx/KgcV8W4Dz2E

Quote:

would say that the gr-osmosdr driver library was compled without support for rtlsdr.

But it may well just be broken. Try it with a new aerial, in a couple of different computers.

273 · 09-06-2015, 10:34 AM

Thanks, the link was helpful in that I know I don't ahve to blacklist any modules as they're not listed:

Code:

rmmod dvb_usb_rtl28xxu rtl2832 
rmmod: ERROR: Module dvb_usb_rtl28xxu is not currently loaded
rmmod: ERROR: Module rtl2832 is not currently loaded

I also know that rtl_test seems to be working.
Oh, yes, at first I hadn't realised there was a start button but I found it soon enough. It's really odd -- I'm definitely hearing "radio" type static but just don't get anything other than noise no matter which channel I tune it to. I'm fairly sure I'd recognise information being received even if I'd chosen the wrong mode or it was digital as information just sounds different to noise in my experience.
I'm certainly tending towards it being broken but can't help thinking I may just be doing something silly, shame I was looking forward to messing about.

michaelk · 09-06-2015, 11:14 AM

The static you hear could be caused by your computer, CFL bulbs or other various electronic devices in your house. A simple wire antenna may not work in this instance. You could try one of the live distributions in the link below to verify it is not a driver problem.

https://www.ab9il.net/software-defin...ml#improvement

Shadow_7 · 09-06-2015, 12:26 PM

GRC aka Gnu Radio Companion has many python scripts for standard signals. You need to run these to convert signals to audio that makes sense to mortals. Otherwise the waterfall stuff tells you where in the frequencies you're currently seeing a signal to tune to that is potentially not noise. The Hak5 crew have a couple youtube videos on it. From what I recall the realtek e4000 chipset was the one that worked well and came with an antennae for $20-ish. The HakRF one is more high end and has broadcasting potential? Which also requires HAM licensing and stuff like that. You might have better luck running another distro or chroot-ing into such an install from your familiar base distro. Many means to an end.

sgosnell · 09-06-2015, 03:24 PM

Or you could just do the easy thing and buy a scanner that works out of the box, guaranteed. Perhaps not as much fun, but if your main interest is listening to radio signals it will get you there.

273 · 09-06-2015, 03:32 PM

Quote:

Originally Posted by sgosnell

Or you could just do the easy thing and buy a scanner that works out of the box, guaranteed. Perhaps not as much fun, but if your main interest is listening to radio signals it will get you there.

I wouldn't mind playing around with ADS-B also if I can get things working and perhaps other things later. Air band scanners seem pretty expensive also. The idea here was to buy a cheap device with a few uses and play a little as well.
I know what you mean though -- hardware would be a lot easier as you know whether it's working or not out of tee box and it would likely work better.

273 · 09-06-2015, 04:46 PM

Turns out that I didn't have the driver loaded in Windows (forgot to check the settings) so that's not a valid test. However, I booted GNURadio live DVD in VirtualBox and I get the same thing in gqrx-sdr -- just static. So, I think my stick must be faulty. Oh, well, might have to buy another. If it turns out to be me that's faulty in the long run I can always use two or pass one on to a friend.

derive · 09-06-2015, 06:56 PM

I think you should use rtl_test , that will supply info about your tuner.
The dvb-t modules should NOT be loaded! ( conflicts with the sdr things ).

That is ok, if you have no driver loaded for it!

You can check ( with an installed usbutils package ) which driver is used for which usb with the "usb-devices" command.

On my system:
#usb-devices
...
T: Bus=05 Lev=01 Prnt=01 Port=07 Cnt=01 Dev#= 4 Spd=480 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=0bda ProdID=2838 Rev=01.00
S: Manufacturer=Realtek
S: Product=RTL2838UHIDIR
S: SerialNumber=00000001
C: #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=500mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
I: If#= 1 Alt= 0 #EPs= 0 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
...

# 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
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...

dump1090 is pretty simple too:
https://github.com/antirez/dump1090
./dump1090 --aggressive --interactive --metric --fix --able-agc --phase-enhance

on my system after a second (my city doesnt have an airport, so these airplanes are above in the air...):

Hex Mode Sqwk Flight Alt Spd Hdg Lat Long Sig Msgs Ti/
-------------------------------------------------------------------------------
49d1cd S 4425 TVQ6952 10631 918 142 46.618 19.097 62 107 0
4baa6a S 3446 THY1ZU 11270 937 130 47.204 18.680 63 63 0

Btw. I regularry use my dongle to listen to NOAA...

gqrx, etc is a little bit buggy, there can be problems with the pulseaudio, resampling, modulation, etc. try the rtl_test and dump1090, they are simple, so better to test the equipment itself.

Don't forget to check the antenna!

273 · 09-06-2015, 07:04 PM

Everything looks fine, rtl_test gives:

Code:

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...
lost at least 84 bytes
^CSignal caught, exiting!

User cancel, exiting...
Samples per million lost (minimum): 3

And usb-devices shows:

Code:

T:  Bus=01 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#=  2 Spd=480 MxCh= 0
D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=0bda ProdID=2838 Rev=01.00
S:  Manufacturer=Realtek
S:  Product=RTL2838UHIDIR
S:  SerialNumber=00000001
C:  #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=500mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
I:  If#= 1 Alt= 0 #EPs= 0 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)

I probably do need to find a bit of wire and make an antenna for testing but I still think it's odd that I'm, as far as I know, inputting the 96.3MHZ for the local RM station and hearing nothing different to any other frequency.

273 · 09-06-2015, 07:11 PM

OK, this is interesting:

Code:

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 
[R82XX] PLL not locked!
Sampling at 2048000 S/s.
No E4000 tuner found, aborting.

Let me try on a VM...

derive · 09-06-2015, 07:14 PM

Is that an analog radio station? Modulation? ( without *ANY* antenna you get nothing, caused by the connector's shield, so yes a piece of wire is also needed ).

So the dongle itself works correctly. The input

Download/compile dump1090, the ATC is fixed modulation and frequency, and there is no soundcard/sound daemon dependency.

I remember that I had a simple fm radio utility it was always send me static noise, and later I found it that it could not use the tuner correctly, so I set the freq in it, but in fact freqency was something default ehh

rtl_test -t works with specific tuner, that's not a problem!

from the manpage:
" -t enable Elonics E4000 tuner benchmark] "