Wrong altitude output for transponder

[airnet]

Hi!

We have a problem that altitude for transponder (Garmin 328) output from Dynon d-100 – encoder is showing cca 300ft wrong. We noticed this because controller was starting to say that we should check our altitude. We cross checked also with other aircraft
We did pitostatic on the aircraft last week and have also cross checked it with altimeter and pitot static tester, so we know now 100% that it shows wrong.
In the manual it says, that you can not “trim or adjust” altitude that Dynon outputs to transponder. So is there any way to solve this problem? Thanks for answer. Iztok, AIRNET

 

[PhantomPholly]

By any chance was the local Altimeter setting around 30.22 or 29.62?

If so, perhaps the altimeter setting was being applied to the output (it is always supposed to calculate altitude as if it were 29.92)?

 

[dynonsupport]

The altimeter setting is never applied to the transponder output. It always sends out the 29.92 altitude.

You can adjust the transponder output, but it also adjusts the main altimeter. Use "ALTADJ" in the setup menu. If your altimeter passed a static check at 29.92, it's impossible for the transponder output to send out anything different.

Are you hooked to the 328 via serial (one wire) or grey code (10+ wires)? If you have the multiple wire connection, you may have a broken wire.

 

[airnet]

Hi!
It is hooked via serial... I will check "ALTADJ" tomorrow and will post findings. Thanks for answer. Iztok

 

[fisac]

Re: no altitude output for transponder through gre

Hi from Spain,
Since I am having problems with the grey code. I want to connect the Garmin GTX 330 strait via serial (one wire).
Can anyone tell me what pin should I use in the GTX 330 to connect the white/blue cable that comes out from the D-180?
Many thanks.

 

[fisac]

We have solved the problem,

Just for the record, to connect the Garmin GTX 330 strait via serial (one wire), connect the white/blue cable (D-180) to pin 24 in the GTX 330, and the White (D-180) goes to any ground on the transponder (even the chassis) to guarantee that the transponder and EFIS have a common ground. You must set the D180 to format "4" and you must set the 330 to "Icarus"

If you're using the encoder converter, make sure you have format set to 1 under the ALTENC setup on the EFIS.

Have a nice day

 

[alschief]

My firend is also having a 300' difference however his is the Dynon D100 display is incorrect by 300'

 

[dynonsupport]

Remember that the altimeter setting is never applied to the transponder output. It always sends out the 29.92 altitude. If the indicated altitude is wrong by that much after a few minutes of warm up AND with the correct altimeter setting applied, the unit should really come back here for a look / calibration.

 

[dynonsupport]

You can adjust the altimeter in the setup menu by as much as 500 or 600 feet, so make sure this adjustment isn't way off as another check. This adjustment affects both the displayed altitude AND the transponder output.