melanpan.nl picked up a used Intellian i4 marine satellite dish on Marktplaats for about €200, against a new price near €4000. The dish uses stepper motors, a quad LNB, and an indoor Antenna Control Unit with Ethernet, WiFi and RS-232.

The ACU expects a boat to tell it where it is and which way it is pointing. Position comes from a built-in GPS, heading comes over NMEA from the vessel. With no boat available, an RP2040 and a TTL to RS-422 module were used to send the ACU fake NMEA sentences.

Intellian supplied the Aptus control software on request. Sniffing the traffic and decompiling the C# code revealed a text protocol with a simple checksum, where pointing means sending GO with azimuth and elevation as integers with two implicit decimal places.

The 40 cm dish uses a prime focus design with a motorised sub-reflector, Intellian’s Dynamic Beam Tilting, which handles small wave corrections so the main motors only make large moves.…