The dual-diode is labelled D20 on the board, and it's inside the triangle formed by the pads for a large version of the Pot - which is depicted. D20 is obscuring the wiper pad for the smaller (standard) version of the pot, which is the same style as R136 the Tx drive pot. The whole shebang sits next to the toroid (that looks like a 6-pin IC) bottom-left on the Wire Up picture on hfsigs site.
