SDR: RTL2832L

Now for something a little different. A couple years ago I heard about the USB-DVB dongles that you could use for software radio, so I picked one up. Of course it sat around in a box until a few weeks ago, when I scratched my computer-building itch by getting an Intel NUC. The NUC DN2820 is kind of annoying due to the UEFI BIOS, but waiting around for a BIOS update paid off and I was able to install Mint 16 (Mate) using unetbootin. I installed gnuradio from the Mint repository, and librtlsdr 0.5.3 from source.

mjng@nuc ~/librtlsdr-0.5.3/src $ lsusb
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 002: ID 8087:07dc Intel Corp.
 Bus 001 Device 003: ID 046d:c063 Logitech, Inc. DELL Laser Mouse
 Bus 001 Device 005: ID 413c:2110 Dell Computer Corp.
 Bus 001 Device 004: ID 413c:1010 Dell Computer Corp.
 Bus 001 Device 007: ID 0bda:2832 Realtek Semiconductor Corp. RTL2832U DVB-T
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

So there it is. One additional wrinkle was that the kernel’s DVB driver was interfering with the RTLSDR library, so I had to turn that off.

mjng@nuc ~ $ rtl_test -t
 Found 1 device(s):
 0:  Generic, RTL2832U, SN: 777711111x

Using device 0: Generic RTL2832U
 Found Elonics E4000 tuner
 Supported gain values (14): -1.0 1.5 4.0 6.5 9.0 11.5 14.0 16.5 19.0 21.5 24.0 29.0 34.0 42.0
 Sampling at 2048000 S/s.
 Benchmarking E4000 PLL...
 [E4K] PLL not locked for 51000000 Hz!
 [E4K] PLL not locked for 2210000000 Hz!
 [E4K] PLL not locked for 1105000000 Hz!
 [E4K] PLL not locked for 1239000000 Hz!
 E4K range: 52 to 2209 MHz
 E4K L-band gap: 1105 to 1239 MHz
mjng@nuc ~ $ rtl_fm -f 103.7e6 -M wbfm -s 200000 -r 44100 - | aplay -r 44100 -f S16_LE
 Found 1 device(s):
 0:  Generic, RTL2832U, SN: 777711111x

Using device 0: Generic RTL2832U
 Found Elonics E4000 tuner
 Tuner gain set to automatic.
 Tuned to 104016000 Hz.
 Oversampling input by: 6x.
 Oversampling output by: 1x.
 Buffer size: 6.83ms
 Sampling at 1200000 S/s.
 Output at 200000 Hz.
 Playing raw data 'stdin' : Signed 16 bit Little Endian, Rate 44100 Hz, Mono
 underrun!!! (at least 16487.192 ms long)

Playing FM radio takes 9-10% of the CPU, which although it is a Celeron, it’s a Bay Trail dual-core Celeron…

One can look for LTE signals and use them to do crystal calibration. I thought this was pretty interesting.

./CellSearch --freq-start 715e6 --freq-end 768e6 --correction 0.9999721 --ppm 10
 Detected the following cells:
 A: #antenna ports C: CP type ; P: PHICH duration ; PR: PHICH resource type
 CID A      fc   foff RXPWR C nRB P  PR CrystalCorrectionFactor
 257 2    739M  1.63k -12.9 N  50 N one 0.99997430722744262699
 161 2    751M   1.6k -30.7 N  50 N one 0.99997423474091573503

There seems to be an amazing amount of info out there now. I’m quite interested to dig deeper.

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