: Around the time of installing the GPS, the groundspeed on the
: KNS-80 began reading 00 KTS under all conditions while flying
: BUT when pinged on the ground--in the aircraft--immediately reads
: the correct value even with the test signal turned so low that the
: DME can barely lock on.

: This has happened in two different late sixties Bonanzas;
: one 28v one 14v.

: The 14v model had a KLN-90B installed, the 28v a 530W.
: Both airplanes have TCADs, both have the KNS-80 talk-only
: suppression line properly connected.

: The DMEs both have great range, often seeing 80-100 mile locks
: below 10,000 feet altitude MSL.

: Things tried in flight that have no effect:

: 1. Stack of 4 KNS-80s rotated into the two airplanes: all
: have same symptom. BTW, RNAV works on all.

: 2. Tune in VOR-DME stations in various directions, various
: distances, various frequencies -- all lock but display 00KTS gs.
: No Y channels 40us pings (.05 channels) tested.

: 3. RNAV tried, GS still 00KTS

: 4. All other radios turned off; no effect

... including transponder? If the transponder is still on and doesn't have the DME suppression wired in it can wreck
havok with the DME (and consequently and distance/speed-related info).

: 5. All other radios REMOVED from stack... still 00 KTS

: 6. All other electrical loads shut off; Alternator shut off;
: still 00 KTS

: 7. Various rpm and attitudes.

: 8. Can't listen to the DME audio in either installation.

: Yet to try: Run the airplane while being pinged on the ground.
: Expected result: Will indicate correctly.

: The DME portion of the box has A+, an antenna, and the
: suppression line coming into the box. How complicated
: can this be? The DME sends serial distance pulses
: internally to
: the main 6800 processor (running at 0.95 MHz) where gs
: is computed along with the trig for RNAV. (There are a lot
: of external lines related to the VOR).

: So what the heck can it be? Get rid of the Bonanza?

: My plane is the 14v one; I've chosen to ignore the problem for
: the last 5 years; the 28v one is being worked on by a local
: shop whose customer is far more anal than I and wants it
: fixed.

: I called King and they are clueless. This one will take
: a lore-based solution. I've written it up in detail, investigated
: in detail but am missing something.

: Am I being persecuted by MI5?

: Bill Hale, Loveland CO

With swapping of multiple KNS-80's, it certainly seems odd. With *everything* else shut off (including transponders,
GPS's, etc) it should "just work" in all modes. I know when we got our KNS-80 we had a listing of all the mods possible and
some of them were fairly important. Maybe the ones you tried all were missing the same mods?

-Cory

--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************