In order to make this a 40-meter transceiver, you have to install specific parts such as capacitors, coils and crystals. Using different values builds a radio for a different band.

Installing the capacitors here is pretty straightforward so I won't dwell on it.

I also faced a challenge I'd never tried before and I hope I manage to document it here properly.

I've seen them but never wound one. It's a lot different than just winding wire around a cylindrical form. The little red/grey donut is a ferroceramic blend (iron powder suspended in a ceramic matrix). The part description is T50-2 which means it's toroidal form a half inch (0.50") in diameter and the 2 means it's the aforementioned blend.

The manual gives a good description of how to wind the coil. The quick description is that you count the number of times the wire goes into the center. Pull each turn tight otherwise output power can be low.

The pictures show the steps for making the transformer. The second coil is very similar but doesn't include a secondary winding.

By the way, in this step, I made a mistake in wiring the second coil to the board. A quick blast with the solder sucker and I was able to fix this before moving on. I'd also installed a cap in the wrong place (C26 in the C6 spot) in stage 1 but that was just as easy to fix.