In the previous two posts I looked at using the RTL-SDR for receiving AIS & ADS-B (Ref.1) on the same local map as well as AIS alone on OpenCPN (Ref.2) using SDRangel (Ref.3). Due to the flexible nature of SDRangel, it is possible to have multiple channel modules within the RTL-SDR sampling bandwidth. So for example for Toronto Harbour, not only can you decode AIS, but Marine Weather as well on one receiver.
Reception of AIS & Marine Weather
Due to the flexibility of SDRangel (Ref.4), it is possible to receive multiple signals using only one RTL-SDR receiver. Figure 1 shows how this is possible. The RTL-SDR can easily provide baseband samples at 2.4Msps. Let’s say we tune the RTL to 162.2MHz, then we can easily capture a bandwidth of 250KHz either side of 162.2MHz. The two AIS channels 87B & 88B and the weather channel lie within this bandwidth. The first AIS channel is -225KHz from 162.2MHz, the second AIS channel is -175KHz away and finally the weather channel is +200KHz away. Figures 2 & 3 show the receiver screen with the RTL-SDR as Source Device Set R0. On the right hand side the Channels modules are located and in the middle the Spectrum. Figure 2 shows the two AIS Demodulators with -175KHz (CH88B) and -225KHz (CH87B) settings. Figure 3 is identical to Figure 2 except the Channels have been scrolled up to show the NBFM module. The AIS settings are the same as in Ref.2. The results from the two AIS demods are displayed on OpenCPN (Ref.5). SDRangel uses the Qt dockable widget set, so it takes a bit of playing around to get used to how the windows can be set optimally and moved.
#1. – “RTL-SDR for AIS & ADS-B on SDRangel Local Map”
#2 – “RTL-SDR for AIS on SDRangel & OpenCPN”
#3. – “SDRangel”
#4. – “SDRangel Quick Start Guide”
#5. – “OpenCPN”
#6. – “ShipsNow”