Assuming you’re talking about the PowerLine/HomePlug module that’s used on the Fathom-X, it’s the RAKwireless LX200V20, which we provide a datasheet for in the Fathom-X technical details.
If you’re after something else then I’d recommend you check the provided schematic and other design files, and ask if what you want isn’t obvious
The last two pages of the LX200V20 datasheet cover the details of the transformer wire and windings. I asked internally if we use an off the shelf one, and was told