Thanks to Tom Hayward <tom@tomh.us> for unblinding me to the hg “add” function. I’ve now submitted a new support suggestion. I think it’d be A Good Idea to add the required instructions to the “Add_A_Radio” section of the blog, since one doesn’t add a whole file very often.

What he said worked a charm, AND correctly diagnosed my problem with the instructions;

I think the issue is the the instructions are written for making
changes to files, and you're trying to add a files. To add the new
file to the patch, try this:

hg add chirp/drivers/ft2.dpy
hg qref
hg export tip

Tom KD7LXL

Declan Rieb WD5EQY