So.. things I've learned in the past 24 hours..

Hooking up the 89B to all the goodies is where it can get interesting.
There are stators and rotors and other thingywhatzits inside the OBS
mechanism of a CDI that can be used to feed info back to the GPS (or
other device like a KX165 or KNS80). In the case of the GPS, it lets
your GPS box know what your OBS is set on.

But.. it may be 30hz 1 phase current or it may be 450 hz 1 phase current
that drives it. King makes both, by the way. And.. something I always
suspected but didnt know until now.. the old stuff was all about
proprietary systems and "use only our stuff" modus operandi.. The worst
surviving offender that I can tell is King (erm.. Honeywell).. but even
that is old news.. the semi new stuff all uses the ARINC standard
format.. and the new new stuff uses RS-232 serial busses. What those
technically entail.. beats me.. but they use it.

Before i realized that the avionics makers of old REALLY REALLY didnt
like "cross-breeding" their stuff with competitors stuff, I found and
bid on an ARC/SPERRY new-old-stock IN-381A vor/loc/gs indicator with
integral converter.. thought.. ok.. this can work with the king.. now im
not so sure.. at least not without some additional information. I want
to say the King drives the indicator with 500 mv and the sperry
indicator is used to being driven at 150 mv. Something to follow up on
lest I let the smoke out of the indicator that I know is dying to
escape. If I cant use it there, I'd like to see if the GPS can drive
it.. maybe maybe not. I think it should, tho, even with the converter,
since it is also a standard ARINC CDI. IF perchance BOTH radios can use
the indicator, then by golly, im getting a second one so at least stuff
PRETENDS to match in a few places.

There truly isnt much out there in the general public about techical
aspects of DIY avionics. Its almost easier to get secrets from a 20th
degree mason than it is to get free tech support or even access to the
manuals to self teach. I understand why: keep the knowledge within the
realm of the dealers and you HAVE to use the dealers/avionics shops to
get the job done.. but I dont have to like it.

So far, the greatest help has been a few key pinouts unrelated to the
89B that show a given other GPS and it interfacing with umpteen other
indicators on a line by line, wire by wire basis. Makes it easy to
reverse engineer what I plan/hope to do.

With regards to the GPS antenna.. so far, everything has been embedded
in the fuselage (as is typical with homebuilt composite types).. well
thats all but done. The primary builder/glassman would not care for a
bump on the roof from the GPS ant, so to verify with the masses, a GPS
antenna can also be completely internal on an epoxy/fiberglass
structure? Im thinkin on the top of the dash "looking" out the window,
even though the window itself is allegedly no less transparent than
fiberglass. The install manual discusses avoidance of the windshield due
to "streaming".. is this solely a metal/conductive a/c event or
something a plastic plane guy should worry about?

So.. if I have a dedicated indicator for the GPS, for an IFR install,
its all about having a few annunciator lights and two switches (OBS/LEG)
and (ARM/Disarm). Maybe I should just home brew the whole thing in
protest, since I wouldnt need a 20+ pin switching relay that retails for
1 AMU plus.

And.. just to let it be known, im not planning on building my coffin.
The experimental I'm involved in isnt to be a hard IFR plane, but then
many light GA planes are barely so, but its still going to be nice to
get in and out of places safely where the visibility isnt THAT good, or
the clouds arent THAT high, and give me a cost effective platform to
finish and maintain that rating in to boot.

Dave