KLN94 -> GTX330 (GND/ALT switching)

P

Peter

Guest
Hi,

I have the above setup. The KLN94 also drives a KMD550; the connection
between the two uses the "enhanced" RS232 data stream so the KMD550
displays the KLN94 flight plan.

The GTX330 transponder is the recent addition. The 330 works but the
auto ground/air mode switching (based on GPS ground speed) doesn't
work.

The avionics shop that did it a couple of weeks ago has offered to fix
it at no charge but they are a long way away and I am trying to fix it
myself if I can. I have the maintenance manuals for the KLN94 and the
GTX330.

The avionics shop has connected the GTX330 to the same KLN94 RS232
output that's used to feed the KMD550, so the "enhanced" data is going
to the GTX330's RS232 #1 input which is set to "GPS" input mode. But
the 330 isn't showing any input.

One possibility is that the additional info in the data stream is
causing the 330 to reject it.

One solution offered would be to set the KLN94 output from "enhanced"
to "standard" but then I lose my KMD550 functionality, which is no
good at all. The avionics place suggested using a different KLN94
RS232 output and setting that output (only) to "standard" but the 94
has only ONE output anyway.

Can anyone shed any light on how this might be made to work? Any info
much appreciated.

A solution might involve a converter which strips out the extra data,
but that is way too much work.


Peter.
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I have a GTX327, and it has a squat switch which is used to switch from
ground to air modes. Maybe your 330 has the same. You may not need the GPS
connected to the 330... I am no expert, I am reading this out of the manual.

By the way, I am interested in making a remote switch for entering
transponder codes. Any info you have on the data protocol in/out of the 330
would be of interest. There are other garmin products that can "tell" the
327 what code to enter, but Garmin is coy with the data protocols.

Bill
 
"Bill Chernoff" <bill@star-techno.com> wrote:

I have a GTX327, and it has a squat switch which is used to switch from
ground to air modes. Maybe your 330 has the same. You may not need the GPS
connected to the 330... I am no expert, I am reading this out of the manual.
Click to expand...
The GTX330 has that option but the cost of this is four figures here
in the UK :)

By the way, I am interested in making a remote switch for entering
transponder codes. Any info you have on the data protocol in/out of the 330
would be of interest. There are other garmin products that can "tell" the
327 what code to enter, but Garmin is coy with the data protocols.
Click to expand...
I have the GTX330 installation manual; that's all. A copy can also be
found at this URL:

http://www.rv7-a.com/manuals.htm

Sounds very useful! Especially if it can be linked to the intercom,
with voice recognition while a button is pressed :)

I've often wondered about having a simple numeric keypad, with a
display showing the current entry, a CLEAR button, and with some "load
this number" buttons next to it marked

COM1
COM2
NAV1
NAV2
DME
ADF
XP

Self explanatory! Would speed up entry massively. I've seen such
panels at exhibitions, apparently for bizjets and not practically
certifiable for GA.

Then all you've got left is loading of flight plans into the GPS,
presently done by twiddling two knobs. That one has been fixed higher
up the market, too :)


Peter.
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Bill,

Maybe your 330 has the same. You may not need the GPS
connected to the 330..
Click to expand...
A squat switch is WAY more expensive than the GPS data transfer.

--
Thomas Borchert (EDDH)
 
Thomas Borchert <borchert_thomas@hotmail.com> wrote:

Maybe your 330 has the same. You may not need the GPS
connected to the 330..


A squat switch is WAY more expensive than the GPS data transfer.
Click to expand...
About US$2000 here in the UK, and most of that is paperwork. Even on
an N-reg; in fact N-reg usually costs more due to the need for stuff
like DER approvals which the U.S. based DER charges out at US$800 per
item :)

I've emailed Garmin to ask whether they need a KLN94 set to emit the
"standard" data rather than the "enhanced" data. I think that's the
key. It would be amazing if I get an intelligent reply to such an
obscure question.


Peter.
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Peter,

Sorry I can't help. We have a 430/330 combo. Works.

--
Thomas Borchert (EDDH)
 
The GTX330 transponder is the recent addition. The 330 works but the
auto ground/air mode switching (based on GPS ground speed) doesn't
work.
Click to expand...
According to the GTX330 Pilot's Guide, the only thing that GND mode does is
turn off transponder replies.

It's my understanding that it is no longer neccessary to turn off or put the
transponder into standby after landing and before departure because with
modern ATC equipment, ground clutter at airports is automatically removed
from radar displays.

Can ATC folks confirm this? I believe I've seen this in various
rec.aviation groups for years now. A quick search of Google Groups confirms
that. Personally, I leave my transponder in ALT mode all the time and have
never had a controller ask me to confirm that it was on.

If the only functionality provided affected by the GND/ALT mode switch is
whether or not the transponder replies to interrogations, then I'd say
forget about trying to get it to read the RS-232 info.

The KMD550 will be much more useful with the enhanced data that the KLN94
sends out. I don't think turning off the enhanced data stream for just the
GND/ALT mode switch is worth it.
 
"Charles Oppermann" <charles@coppersoftware.com> wrote:

The KMD550 will be much more useful with the enhanced data that the KLN94
sends out. I don't think turning off the enhanced data stream for just the
GND/ALT mode switch is worth it.
Click to expand...
I agree 2000%.

For the record, I have just got this piece of info

The KMD 540 takes Enhanced RS 232 flightplan information from the KLN 94 pin
2, to display flightplan waypoints, holding patterns and procedure turns.
The GTX 330 should be looking for raw GPS data from the KLN 94 pin 6. That
is direct from the GPS receiver module. The GTX 330 will not get what it is
needing from pin 2 and will be confused by the Enhanced Data.
Click to expand...
direct from somebody who knows the products intimately. So, instead of
using the KLN94's pin 2 (standard RS232 output) one has to use pin 6
(spare RS232 output).

I haven't tested this yet; the trip to the avionics shop and back
involves 2 days' travelling :) But if I don't report further, it
worked.


Peter.
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