Well. I wired up the mating connector that way, and they definitely are not numbered that way.
If we assume numbered this way (where K is the key way & looking at the connector on the back of the GP33):
9 K 10
6 7 8
3 4 5
2 1
I get a good signal between pins 3 and 2 when pin 3 is connected to DB-9 pin 2 and pin 2 is connected to DB-9 pin 5. Plugging into my ancient laptop with a COM port & booting HyperTerminal gives me good NEMA sentences.
If I connect pin 1 above to pin 2 of the DB-9, leaving pin 2 on DB-9 pin 5, then I get gibberish on HyperTerminal. Connecting pins 9 & 10 ( my original assumption as to which pins were 1 White & 2 Blue) to the DB-9 got me nothing at all. I don't remember if I swapped pins 1 & 2 with DB-9 pins 2 & 5 after I got pin 3 to give me good data.
As I recollect, most computer RS-232 ports will read NEMA-183 output, but I could be wrong on that.
In any case, connecting pins 1 & 2 above to my NEMA-183 listeners didn't show any data. Connecting pins 2 & 3 to one of my NEMA listeners (my old fixed mount VHF radio) shows me position data.
If I short pins 9 & 1, 6 & 1 or 5 & 1 (again, using the above diagram), then I get a MOB event. Shorting other combinations of pins does not give me a MOB event. I don't remember if I checked them all.
So, my big question is - what is the proper pin designation on that NEMA connector on the GP-33? Are what I have labelled pins 2 & 3 really pins 2 & 1 (TH-C & TD-H) or are they SG & SD?
Also, if you swap TD-H & TD-C, with DB-9 RD & SG, do you get a gibberish signal?