* Changed from the tps61071 to the tps61200 boost converter.   Higher current sourcing ability, lower drop out on the input power.   This chip also supports a 'power save' mode which will be useful in this application.

* Added support for a BMP085 barometer, more instrumentation is a good thing in this application.

* Removed the pads for selecting serial/i2c on the GPS.   i2c will be sufficient and the serial port will be needed for programming and potentially supporting a TTL/Serial camera module.

* Changed the layout of the low pass filter for on the RF side of the circuit.

* Corrected the routing of the VCXO to the Si4463.   I was actually hoping to get some 4063's as the RX stage is wasted, unfortunately the usual suppliers don't have this in stock.   As it is I can only get a couple of the VCXO's for now.  Some of the changes I've made will allow for some reorganisation of the board as it is...   but I have to stop somewhere!