Ortac_AIS is an advanced Windows dual channel AIS DSP receiver and message decoder. It is capable of decoding up to 25 messages per second simultaneously on channels A and B. It has been tested on Win7 to Win11.

There are three versions of the programme, each tailored for a family of radios SDRPlay, AirSpy or RTL-SDR.
Various intermediate workings of the receiver can be examined by opening the sub windows (forms).
This software is intended for educational and personal use only. The Ortac software must not be relied on for navigational purposes; or any other purpose that might have causal life threatening consequences that may be dependent on the failure or error of this software (Ortac_AIS).
In order to receive AIS signals it is recommended that some form of external antenna is used:- eg a Discone or ½ vertical wave dipole cut for 162MHz.
The outputs of the Ortac receiver are NMEA sentences that can be streamed via UDP and/or TCP to local mapping programs or externally to sites such as www.marinetraffic.com.
RFBits does not guarantee the validity of any data exported.
The software decodes both short and long messages. Vessel names are collected from class B Type 24 and class A Type 5 messages and stored in a text file ‘Vessels.csv’.
The Decodes window shows a log of decodes, displaying MMSI, vessel names, position and time stamp. If the Lat-Long of the receive station is added under the ‘Distance Calc’ option, then the distance and bearing can be displayed. A right click menu allows the position to be shown on Google Maps, looked up on marine Traffic or added to AIS filters.

Important note.
This Issue ( of the software, unlike previous versions does not have a kill date. The software is issued as donationware, if you find this software of use, please consider a donation.

Features: –

  1. Dual Channel, upto 25 messages per second on each
  2. Very sensitive, decodes at less than -120dBm
  3. MMSI, Vessel Name and position decodes
  4. FFT and Demod screens to analyse signals
  5. UDP and TCP NMEA output
  6. Logging functions
  7. Low CPU load

You can read the full manual, which describes the functions and operation of the software here : –

Ortac_AIS has three build variants, each optimised to work with a family of radios: –


Works with the SDRPlay series of radios : –

Read more about SDRPlay radios at https://www.sdrplay.com/products/


Works with RTL2832u devices which have the Rafael Micro R820T, R820T2 or R860 RF tuner, examples are : –

Read more about RTL-SDR at https://www.rtl-sdr.com/about-rtl-sdr/


Works with these AirSpy radios : –

Read more about AirSpy radios at https://airspy.com/.