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Can a GTN650 be interfaced with a GTX330 transponder?

Apologies for not being able to research before asking, but I’m in Kenya, with my avionics guy, fitting a GTX 330 to a C182P. Internet is unreliable, and I can’t contact Garmin Support. We’re currently marooned at Wilson, as t’ponder is compulsory to leave the zone.

In practice, can a GTX 330 be interfaced with a GTN 650?

Actually, I can’t see the point of remote controlling the 330, so maybe it’s not an issue.

Last Edited by 2greens1red at 18 Nov 08:46
Swanborough Farm (UK), Shoreham EGKA, Soysambu (Kenya), Kenya

Yes, with bi-directional RS232.

Avionics geek.
Somewhere remote in Devon, UK.

It depends on what connection you want to achieve. Is this for ADS-B OUT?

The GTX330 also needs pressure altitude, from some sort of encoding altimeter. This can come via RS232 or via ARINC429 if serial, or via gray code (10 wires). Most altitude encoders used in GA are gray code. But if that pressure altitude already goes to a GTN650 then it may (wigglyamp will know all of this) be possible for the GTN650 to send it to the GTX330 (probably via ARINC429).

If a txp is mandatory, it will be just Mode C so you need just pressure altitude. If the GTN has been installed correctly, the pressure altitude will already go to it. So it is a matter of establishing whether / how you can get it to output that. If ARINC429 it will be some Label xxx and the GTX330 will recognise that. In the 330 you need to configure the appropriate serial port and what to expect on it.

Administrator
Shoreham EGKA, United Kingdom

Thanks, Wiggly.

Peter, no, I think that would need the upgraded model of the 330 (documentation not at hand).

Edit
We’re using an ACK-30 encoder, junking all the old wiring, and renewing from scratch.

Last Edited by 2greens1red at 18 Nov 09:02
Swanborough Farm (UK), Shoreham EGKA, Soysambu (Kenya), Kenya

You can actually get Mode S data to come out of the (any version) GTX330, and you can do automated GND/AIR mode switching based on GPS ground speed, but you don’t need that. You just need the pressure altitude connected up.

Administrator
Shoreham EGKA, United Kingdom

2greens1red wrote:

In practice, can a GTX 330 be interfaced with a GTN 650?

This is exactly the setup we are running.
As I remember we paid a bit extra to the installer to update the software on the GTX330 to allow for the communication with the GTN650. We can remote choose the squawk code on the GTN650, but I always use direct entry on the GTN650.

pmh
ekbr ekbi, Denmark

Some wiring diagram pieces from the GTX IM

There is this gotcha

This is from the GTX330 IM

You need to do a lot of config to get this stuff to work. The avionics guy needs to know what he is doing.

The above assumes the GTN is getting pressure altitude. It may not be, in which case you need to wire that up, possibly directly to the GTX.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

You need to do a lot of config to get this stuff to work. The avionics guy needs to know what he is doing.

It’s not difficult. The GTN IN/OUT RS232 ports needs to be set to GTX MODES #1, and the GTX ports need to be set to REMOTE.
On the GTN, the ‘More RS232 CONFIG page needs to be selected and the ’Send ALT to XPDR’ should be enabled.
If the GTN doesn’t already have a pressure altitude source then as already proposed, a direct connection from an altitude encoder will be required.

Once the GTN configuration has been completed, don’t forget to go back to the configuration home page and ‘UPDATE CONFIG MODULE’.

Avionics geek.
Somewhere remote in Devon, UK.

Bear in mind this GTX330 might be an old one, FWIW, so firmware versions might not be anywhere near current.

I have one from 2005, for example. I was an early adopter But mine gets pressure altitude via gray code which goes back to this chap who always did things right.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

You can actually get Mode S data to come out of the (any version) GTX330

I believe you need a GTX330ES model to get Mode S out. That’s what the ES gives you. At one point converting a straight GTX330 to GTX330ES was a $2000 upgrade.

LSZK, Switzerland
18 Posts
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