Real world tests of AIS
sdr receivers, targeted for sailors are scarce. You might find these results helpful.
1 – SDR – 4 elements collinear antenna
rigged up close to the mast/spreader à
rtl-sdr V2 dongle à
Macbook, 10.11.6, rtl_ais (default parameters), OpenCPN
2 – VESPER – commercial VHF antenna
on a stern rail à
Vesper XB-8000 transponder à
Macbook, 10.11.6, OpenCPN
moored in a marina, 1 mile from the sea shore, no direct line of sight to the sea; 3 miles away from a commercial
harbour with no direct line of sight and with a busy city area between; must of the AIS
class A used as targets for this test were underway to or from that commercial harbour; 24 hours test with both systems always on, samples at random intervals, balanced consecutive trials of 6+6 minutes for the 2 systems ; temperature near the rtl- sdr dongle, 21-25 ºC.
Data quite stable across the 24 hours test. Descriptive statistics of 2 samples in the attached file. VESPER clearly outperforms SDR in all recorded parameters: nº of targets, maximum range, warm up time to reach the maximum target number, refresh rate of an AIS target. Connecting the SDR to the commercial VHF
antenna drastically reduced range (to only nearby moored vessels up to 0,3 miles). Same performance of Vesper regardless of the type of antenna. Playing with the gain and sampling rate of the rtl_ais decoder, not done here, might help achieving better performance. With a clear line of sight, the RTL performance should be far better, anyway. Of course, there is not an “always best” performance standard for an AIS system; Therefore, the performance of the SDR, in this test, with default parameters, might be more than enough, or not, for a given skipper/goal/navigation area.
SDR might be useful both as a backup to our boat
and as the standalone system for delivering or chartering other boats for a few days. In a previous 1200 miles passage
the VESPER needed to be rebooted, to overcome AIS or Wifi
troubles, about once per day. It is unlikely to achieve a better reliability
with an SDR. So, for an intensive use, particularly if in hot areas, better to buy a spare rtl-dongle and of an improved design.