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  #1  
Old 11-03-2018, 07:52 PM
Handclutch Handclutch is offline
 
Join Date: Feb 2015
Location: Bendigo, Australia
Posts: 66
Default GPS NAC velocity

I am installing a Trig TT21 transponder and using a Garmin 420 W for the ADSB feed. Setup in the Trig is asking for the Navigational Accuracy Category for velocity (NACv) for the Garmin. Says it will be in the GPS installation manual but I can't find it. Has anybody come across it? It will be the same for both the 420 and 430 W.

Jack
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  #2  
Old 11-04-2018, 10:55 AM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
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Have you tried calling Garmin?
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  #3  
Old 11-04-2018, 11:08 AM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
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Quote:
Originally Posted by Handclutch View Post
I am installing a Trig TT21 transponder and using a Garmin 420 W for the ADSB feed. Setup in the Trig is asking for the Navigational Accuracy Category for velocity (NACv) for the Garmin. Says it will be in the GPS installation manual but I can't find it. Has anybody come across it? It will be the same for both the 420 and 430 W.

Jack
10 meters/sec

However for the trig:
NOTE: If the Garmin ADS-B Plus protocol is used then the NACv is set dynamically by the
Garmin GPS unit. This manual configuration item is ignored.
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  #4  
Old 11-04-2018, 06:40 PM
Handclutch Handclutch is offline
 
Join Date: Feb 2015
Location: Bendigo, Australia
Posts: 66
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Thanks, Walt. The Trig will accept ADS-B Plus - problem solved. (This forum is a great resource!)

Jack
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  #5  
Old 11-04-2018, 07:51 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
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BTW, here in the US the TT-21 doesn't have enough power to meet the US ADSB specs. I presume you checked, it's legal in Australia?
PS I'm using a TT-22 and a G420W, to meet US ADSB-out rules. Works great.
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  #6  
Old 11-05-2018, 06:05 AM
Handclutch Handclutch is offline
 
Join Date: Feb 2015
Location: Bendigo, Australia
Posts: 66
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Thanks, Bob. Yes, the TT21 is legal in Oz up to 15000 and below 175 knots. After that you need the TT22 (class 2 transponder). The TT22 transmits at a higher power.

Jack
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  #7  
Old 11-05-2018, 04:11 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
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Interesting. I checked my Freeflight setting, and it is called out at 3 M/sec. I would have expected the Garmin and Freeflight settings would be closer to each other.
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