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#Airport drivers for ubuntu software
#Airport drivers for ubuntu series

We set the gain to a value and record about half a day of data.

We tuned the gains carefully and did some more experiments which we will share with you in one of our next blog posts. On the other hand, if you set the gain too high, then clipping appears on the ADC and you get “noisy” recordings. If you set the gain too low, you will receive noisy audio signals as there is not enough energy and your signal will be coded only in a few lower bits by the ADC. Ideally you should tweak only the analog gain closest to the antenna. You should set the gain as low as possible in general. Please consult documentation, support, or community for your device to find out block diagrams, gain controllers and proper settings. RTL-SDR has 1 gain, SRDplay RSP1A has 2 gain controls. There may be more gain controllers for your device. If you set it too high, then the signal starts to be choppy. Tune this parameter ( 128 / 256 / 512 / 1024) and watch the load and signal quality. Good practice is that for wider bandwidth the FFT size should be larger. The larger the value (in power of 2) the slightly better the signal but the more CPU power is needed. fft_sizeįFT size is an internal parameter that impacts the signal processing. The first one is gain and the second one is fft_size. There are 2 more parameters that have an impact on the audio quality. Sample_rate = 900100 #bandwidth in Hz around centerfreqįilename_template = "PRAGUE_Tower_134_550MHz" Gain = 15 #Every type of device has different gain settings Sample of rtl-airband config for RTL-SDR device. The solution was to change the central frequency. We have tried to change the bandwidth and gain but it did not help. It may happen that a strong source near you may leak into your recording (even if it is on a different frequency).

The problem is called ghosting (thanks to ). We had strong harmonic distortion in the audio signal.

However we found a problem with recording the Tower (note: our setup is very close to the airport so we have a strong signal). We limited the bandwidth of RTL-SDR and put the center frequency the same as the frequency of the Tower ( 134.55MHz). We set the bandwidth of RSP1A to 5MHz which gave us 14-bit sampling precision (better audio quality). RSP1A covered the group of channels around 123MHz and RTL-SDR took care of the Tower on 134MHz. Finally, our solution was to use SDRplay RSP1A and RTL-SDR (on two separated antennas). We analyzed the traffic on the channels and found out that the Radar on 127MHz is a “copy” of Radar on 120MHz. We would need about 16MHz bandwidth to cover them all. One of the Radars and the Tower are the problematic ones as they are away from the rest. Sample_rate = 9.00 #bandwidth in MHz around centerfreqįilename_template = "BRNO_Tower_119_600MHz" Gain = "IFGR=20,RFGR=2" #Every type of device has different gain settings Sample of rtl-airband config for SDRplay RSP1A device would look like the following: country = "Czech Republic" ĭevice_string="driver=sdrplay,serial=xxxxxxxxxxxxxx" The “bandwidth” of the SDR - sampling frequency - was chosen wider than needed to overcome possible distortions on the edges. We placed the central frequency in the middle. The green boxes indicate 25kHz bandwidth of one channel. See our configuration in the following figure: So to fully cover the LKTB, we need a pair of RTL-SDRs or one RSP1A. You can notice that the distance between LKTB_TWR and LKTB_APP is 7.75MHz which is much larger than 2.5MHz supported by the RTL-SDR but smaller than 10.6MHz supported by the SDR RSP1A (see previous blog post regarding more technical information). We checked available on-line resources and found main frequencies used in LKTB. If some frequencies are too distant, you may use two SDR devices (we are also using this setup). First, you need to identify VHF frequencies you want to record and decide what is your central frequency and bandwidth. You need to do several steps to set up the SDR.

#Airport drivers for ubuntu software

You should end up with a Linux distribution with installed SDR drivers and RTL-airband software running ( ). Please follow the instructions at website. We will aim at software installation and SDR settings.

#Airport drivers for ubuntu series

Welcome to the next blog post from our series of “How to set up an ATC voice recorder”.

Blog 3: What is the best SDR hardware choice for ATC.

Blog 2: Where to place your antenna for ATC recordings.

Blog 1: Basic terminology and hardware setup description for ATC listening.