Kalibrate and rtl_test

M

Malpractice

New Member
I have a Pi and a RTL2832U USB stick. I believe it is the version 2 (blue colour not black).

Just fine tuning my setup and wondering if I am doing this correctly, I am getting conflicting results.

I read somewhere that kalibrate doesn't like the new RTL2832U v2 and that I should use rtl_test instead.
kal says -30 ppm
Rtl_test +55 ppm

Help!


Code: 
pi@localhost ~/kalibrate-rtl $ kal -s GSM900
Found 1 device(s):
  0:  Generic RTL2832U OEM

Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Exact sample rate is: 270833.002142 Hz
kal: Scanning for GSM-900 base stations.
GSM-900:
        chan: 84 (951.8MHz + 29.986kHz) power: 31981.56
        chan: 92 (953.4MHz + 30.180kHz) power: 29258.01
        chan: 107 (956.4MHz + 30.400kHz)        power: 47973.20
        chan: 111 (957.2MHz + 29.637kHz)        power: 48579.33
        chan: 115 (958.0MHz + 29.874kHz)        power: 39259.08


pi@localhost ~/kalibrate-rtl $ kal -c 111
Found 1 device(s):
  0:  Generic RTL2832U OEM

Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Exact sample rate is: 270833.002142 Hz
kal: Calculating clock frequency offset.
Using GSM-900 channel 111 (957.2MHz)
average         [min, max]      (range, stddev)
+ 29.655kHz             [29626, 29686]  (60, 16.046793)
overruns: 0
not found: 0
average absolute error: -30.981 ppm


pi@localhost ~/kalibrate-rtl $ rtl_test -p
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.
Reporting PPM error measurement every 10 seconds...
Press ^C after a few minutes.
Reading samples in async mode...
real sample rate: 2047897 current PPM: -50 cumulative PPM: -50
real sample rate: 2048105 current PPM: 52 cumulative PPM: 1
real sample rate: 2048091 current PPM: 45 cumulative PPM: 15
real sample rate: 2048125 current PPM: 61 cumulative PPM: 27
real sample rate: 2048149 current PPM: 73 cumulative PPM: 36
real sample rate: 2048118 current PPM: 58 cumulative PPM: 40
real sample rate: 2048101 current PPM: 50 cumulative PPM: 41
real sample rate: 2048118 current PPM: 58 cumulative PPM: 43
real sample rate: 2048113 current PPM: 56 cumulative PPM: 45
real sample rate: 2048139 current PPM: 68 cumulative PPM: 47
real sample rate: 2048105 current PPM: 52 cumulative PPM: 47
real sample rate: 2048113 current PPM: 55 cumulative PPM: 48
real sample rate: 2048106 current PPM: 52 cumulative PPM: 48
real sample rate: 2048128 current PPM: 63 cumulative PPM: 49
real sample rate: 2048110 current PPM: 54 cumulative PPM: 50
real sample rate: 2048123 current PPM: 60 cumulative PPM: 50
real sample rate: 2048106 current PPM: 52 cumulative PPM: 50
real sample rate: 2048113 current PPM: 55 cumulative PPM: 51
real sample rate: 2048139 current PPM: 68 cumulative PPM: 52
real sample rate: 2048104 current PPM: 51 cumulative PPM: 52
real sample rate: 2048113 current PPM: 55 cumulative PPM: 52
real sample rate: 2048127 current PPM: 62 cumulative PPM: 52
real sample rate: 2048121 current PPM: 59 cumulative PPM: 53
real sample rate: 2048103 current PPM: 51 cumulative PPM: 52
real sample rate: 2048121 current PPM: 59 cumulative PPM: 53
real sample rate: 2048113 current PPM: 55 cumulative PPM: 53
real sample rate: 2048129 current PPM: 63 cumulative PPM: 53
real sample rate: 2048116 current PPM: 57 cumulative PPM: 53
real sample rate: 2048093 current PPM: 46 cumulative PPM: 53
real sample rate: 2048131 current PPM: 64 cumulative PPM: 54
real sample rate: 2048110 current PPM: 54 cumulative PPM: 54
real sample rate: 2048131 current PPM: 64 cumulative PPM: 54
real sample rate: 2048116 current PPM: 57 cumulative PPM: 54
real sample rate: 2048094 current PPM: 46 cumulative PPM: 54
real sample rate: 2048139 current PPM: 68 cumulative PPM: 54
real sample rate: 2048112 current PPM: 55 cumulative PPM: 54
real sample rate: 2048124 current PPM: 61 cumulative PPM: 54
real sample rate: 2048091 current PPM: 45 cumulative PPM: 54
real sample rate: 2048132 current PPM: 65 cumulative PPM: 54
real sample rate: 2048106 current PPM: 52 cumulative PPM: 54
real sample rate: 2048130 current PPM: 63 cumulative PPM: 55
real sample rate: 2048097 current PPM: 48 cumulative PPM: 54
real sample rate: 2048124 current PPM: 61 cumulative PPM: 55
real sample rate: 2048134 current PPM: 66 cumulative PPM: 55
^CSignal caught, exiting!

User cancel, exiting...
Samples per million lost (minimum): 0
 
I'm trying to replicate your results, on a laptop/RTL but cannot get any signal at all using kalibrate-rtl !
Does this help? ..
https://github.com/steve-m/kalibrate-rtl/issues/8

It, and a reddit thread, suggest you need to give kalibrate a rough estimate of the ppm error to start.
Anyway, thanks for the pointers to calibration routines.
(I'm presently trying to see if SDR# raw waveform display can show me the way to proper wire-length tuning )

Best.
 
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