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Old 09-21-2019, 07:14 PM
rwarre rwarre is offline
Join Date: Jul 2007
Location: Wray, Co
Posts: 600
Default 2 transponders with adsb

Went flying today IFR for practice. The ATC controller said I was showing up as an IFR and a VFR target. He thought I had 2 transponders. Turned off my adsb and the VFR target went away. I have the Echo UAT and it gets the position from a Garmin 430w. My iefis is the MGL explorer. Has this ever happened to anyone?
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Old 09-21-2019, 07:59 PM
Radomir's Avatar
Radomir Radomir is offline
Join Date: Jan 2005
Location: Charlotte, NC
Posts: 1,524

Is your UAT going into anonymous mode on its own (and not really picking up TXP code properly)?
RV-7A sold
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Old 09-22-2019, 12:50 AM
WingsOnWheels WingsOnWheels is offline
Join Date: Mar 2009
Location: Plano, TX
Posts: 2,112

How is the echo setup to receive squak? Are you sniffing it from xponder reply, or sending it over serial? What trandponder are you using?

I have mine getting squak from the gtx330 and alt from the dynon, both via serial data through the uavionix serial multiplexer.
Colin P.
RV-6A #20603
Complete 5/10/19
I donate every year on my B-Day (in Dec), but donated early in Sep'19.
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Old 09-22-2019, 06:44 AM
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DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 9,795

Yes, last weekend I was inbound to 08A from the south, squawking 1200/anonymous. After dialed up MGM approach and entered an assigned code, the controller responded with the usual, then asked if I had another aircraft in formation, as he was seeing the assigned code as one target and a 1200 target also.

We talked about it a bit and then he had to move on to other traffic. I got the impression that the 1200 target had disappeared from his scope.

Garmin GTX-327 and GDL-82.
Dan Horton
Barrett IO-390
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Old 09-22-2019, 05:20 PM
rwarre rwarre is offline
Join Date: Jul 2007
Location: Wray, Co
Posts: 600

I have the Echo UAT and it sniffs a Garmin 430W. I also have a Garmin 327 transponder which get the grey code from the MGL Efis.
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Old 09-30-2019, 04:41 PM
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DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 9,795

Originally Posted by RV8JD View Post
Earlier this year after a friend installed a Garmin GDL 82, we flew near each other while he switched Anonymous Mode on and off to check its operation. His transponder is a GTX 327. I captured this ForeFlight screenshot showing him immediately after he switched Anonymous Mode off.

Note the two targets on top of one another, one showing his N-number and one showing "VFR". After several seconds the "VFR" target disappeared and only the N-number target showed. We tried this a few times (him switching between Anonymous Mode on and off) and two targets would show up from a few to several seconds until one dropped off. We attributed this to latency/overlapping data in the ATC system, until the older, stale data dropped from the system.
Sorry Carl, missed your response. Your account exactly matches what MGM approach was describing.
Dan Horton
Barrett IO-390
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Old 10-01-2019, 10:03 AM
Flyingleap Flyingleap is offline
Join Date: Nov 2012
Location: Cincinnati,Ohio KHAO
Posts: 129
Default Same here!!

I have a GTX327 and GDL82 . The same ATC claim of two targets in the same position after changing code from 1200 to ATC request. This has happened twice this month.... John
John R Prince
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Old 10-01-2019, 11:17 PM
NewbRVator NewbRVator is offline
Join Date: Jul 2018
Location: CA
Posts: 261

Happened to me too with a GNX375. Went from 1200 to an assigned code I picked up after departure from ARTCC. I was climbing so the "old" me was lower but very near my position but then like magic I disappeared and the new me flew off into the sunset.

Pretty cool eh? A real time machine. Maybe a hole in the fabric of space time continuum.
20 dues paid member since 2018
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Old 06-17-2020, 06:43 AM
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rv767 rv767 is offline
Join Date: Jan 2005
Location: USA
Posts: 65
Default R U in formation?

This just happened to me on an IFR flight to Texas last week. ATC kept asking if I had someone in formation with me. (I'm getting a good report from the FAA ADSB website and "IN" is good as well) but when I squawk other than 1200 on my TXP, the ADSB stays on 1200 giving conflicting traffic to ATC.

Garmin GTX 327
GRT Sport SX
uAvionics Echo UAT-Safefly 2020

Anybody have new info on this subject? DanH, what did you find out?
Neal RV-7 Flying--2020 VAF
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Old 06-17-2020, 07:55 AM
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BCP Boys BCP Boys is offline
Join Date: Oct 2011
Location: Kennesaw, Ga
Posts: 855
Default Latency

Since there are so many examples of this happening, on so many different platforms, I'm wondering if this could possibly be a network latency issue between the ground station submitting the new identification to the ATC database cross referencing the ICAO code with the newly assigned number. Basically it seems like its taking several minutes to sync the data and overwrite the previous code, 1200, or VFR, or whatever it was. If this happens again to someone and ATC isn't busy, I wonder if you asked for another code and changed it, they would probably see the previous code as being in formation with you.
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Supporting VAF since the first visit
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