DIY FPV backpack Part 1 - the theory and design

In part 1 of the FPV backpack project I take a look at the design of the electronics and what each component does, plus how they are all interconnected.
You don't have to understand all this stuff but I thought some people might be interested.
Hopefully the boards will be here in a week or so but next week I'll be posting the schematic and PCB layout files for those who want to etch their own.