I have read a lot about this subject and can see how it works. Most of the material is 50+ years old and it is really mostly quite simple.
But I need some specific advice for something I am building.
It is a box which takes in serial data containing an angle, 0 to -180 (for western headings) or 0 to +180 (for eastern headings).
Yes, south can be both -180 or +180 but that's not a problem :)
I am using two DACs to generate the two output sinewaves, 400Hz. These are called X and Y.
I could optionally also generate the reference one, possibly called Z I think, also 400Hz but for reasons unrelated a lot more power capability is needed.
What I can't get my head around is how to arrange the phases.
I *think* the reference would be an INPUT to this box, and the angle is represented using the two other sinewaves, which I will be generating. The phase will be relative to the reference, somehow.
I can't work out whether X and Y carry the heading between themselves or whether they are shifted symmetrically around the reference, or whatever.
The signals will go to various instruments used in aviation, for testing.
Many thanks in advance for any info. I am sure the answer is very simple!