Low quality FM transmit "HELLO WORLD" on an iceblink40-hx1k board, without using a PLL. Total size 74 SB_LUTs. See source code for documentation.
A (dated) picture of the design can be seen here here.
Designed for compilation with iCECube2, with Lattice LSE as Verilog compiler. Placement, and use of cascaded LUTs, is vital in this design.