uSDX smd: An effecient and lightweight HF radio

Goals of this particular build:

Light enough for backpacking (5oz without batteries, 12oz with batteries)
Effeciency for extended operation on battery power
High-quality SSB audio
Compatible with 3.5mm TRRS phone audio cable, for running digital modes on a phone or small laptop
Inexpensive hardware - under $50 including PCB
Reasonably solderable at home