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@@ -5,6 +5,19 @@ based on this code and designs is fully functional, but there is still a long wa
 
 I intend to publish a blog (linking to and from here) as the project evolves.
 
+## Overall architecture
+
+On the hardware side, the design is based on two Silicon Labs 4463 transceiver ICs and an STM32F302 ARM Cortex M4 microcontroller.
+The GPS is a GlobalTop "LadyBird" unit, but any decent GPS module with NMEA and PPS output would work.
+
+On the analog RF side, the receiver incorporates an active bandpass filter with an NXP BGA2869 LNA, and a SkyWorks 66100 Front End module (PA/switch).
+The transmitter output is nominally 0.5Watts (+27dbB) and it has a verified range of 5 nautical miles.
+
+The system is powered entirely from a USB connection which also delivers NMEA (GPS + AIS) data to the host.
+
+### The nitty gritty
+Physically, the unit is designed as two overlaid PCBs, joined together with standard 0.01" male/female pin headers, just like
+Raspberry Pi and Arduino hats. One PCB holds the logic and GPS stage and the other PCB hosts the RF stage.