diff --git a/Correcting-the-frequency-offset.md b/Correcting-the-frequency-offset.md index 859fd77..d865127 100644 --- a/Correcting-the-frequency-offset.md +++ b/Correcting-the-frequency-offset.md @@ -15,13 +15,13 @@ This will install the `kal` utility to your computer. -Use the stock antenna of the tuner. - **Step #1** is to scan for GSM channels: kal -g30 -sGSM900 -v -**Note:** you may have to set the band (`-s`) regarding your location, country. Available bands: `GSM850, GSM-R, GSM900, EGSM, DCS, PCS` +**Note #1:** you may have to set the band (`-s`) regarding your location, country. Available bands: `GSM850, GSM-R, GSM900, EGSM, DCS, PCS` + +**Note #2:** you can use the stock antenna of the tuner. The output of this command should look like this: @@ -46,4 +46,40 @@ The output of this command should look like this: chan: 83 (951.6MHz - 24.438kHz) power: 430946.94 chan: 112 (957.4MHz + 24.397kHz) power: 857829.53 +**Step #2** is to select the most powerful channel, and use it to calculate the PPM value: +> chan: **112** (957.4MHz + 24.397kHz) power: **857829.53** +...so we use channel 112: + + kal -g30 -c112 -v + +The output of this command should look like this: + + $ kal -g30 -c112 -v + 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 + Setting gain: 30.0 dB + kal: Calculating clock frequency offset. + Using GSM-900 channel 112 (957.4MHz) + offset 1: 24292.79 + offset 2: 24233.90 + offset 3: 24300.03 + offset 4: 24252.50 + offset 5: 24212.21 + offset 6: 24287.63 + offset 7: 24237.00 + (...) + offset 96: 24244.24 + offset 97: 24327.92 + offset 98: 24260.77 + offset 99: 24314.49 + offset 100: 24262.83 + average [min, max] (range, stddev) + + 24.268kHz [24218, 24319] (100, 28.573065) + overruns: 0 + not found: 0 + average absolute error: -25.348 ppm