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Help me understand missing traffic w/MLB100

Printed From: Avidyne
Category: Avidyne General
Forum Name: SkyTrax Series ADS-B Receivers & Transceivers
Forum Description: Topics on the Avidyne SkyTrax 978 MHz Receivers & Transceivers
URL: http://forums.avidyne.com/forum_posts.asp?TID=1384
Printed Date: 09 Dec 2019 at 6:48pm
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com


Topic: Help me understand missing traffic w/MLB100
Posted By: jimmyz80
Subject: Help me understand missing traffic w/MLB100
Date Posted: 26 Aug 2017 at 12:19am
So I'm a little bit stumped, and maybe I have unrealistic expectations of the various FAA traffic systems.  I'm hoping someone here can help me understand what's going on here.

For context I have an AXP322 for ADS-B 1090 OUT, and an MLB100 for 978 IN.  I also have L3 Skywatch TCAS in my plane, so I have the luxury of comparing TCAS traffic with ADS-B traffic.

What I've been seeing is LOTS of traffic that I can see on TCAS, but I never ever see it on ADS-B.  My understanding is that my setup should:

A) Receive direct reports from aircraft equipped with UAT/978 OUT hardware.
B) Receive ADS-R rebroadcast traffic from ground stations, for 1090 targets since the MLB100 doesn't have 1090 IN.
C) Receive TIS-B traffic from ground stations, for Mode-C targets that aren't participating in ADS-B.

So my question is, why do scenarios B and C seem to not be working for me?  Are the ground stations really unreliable?

I requested an ADS-B Performance Report for one of my flights this evening where this situation occurred multiple times, and I see two important things:

A) OUT capability is correctly listed as 1090 and IN capability is listed as UAT.  This should indicate that the FAA systems know I need 1090 targets rebroadcast to me.

B) TIS-B Client % is listed as 94.5%, which should mean that only a very small portion of my flight would have been a "dead zone" for ground station traffic.

Any ideas?


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2006 Cirrus SR22 - IFD540 IFD440 DFC90 AXP322 MLB100



Replies:
Posted By: DavidBunin
Date Posted: 26 Aug 2017 at 6:56am
How is the MLB wired to your IFD540?  Is it through the serial data interface, or is it through the ARINC 429 interface?  What is your IFD configuration for data ports?


Posted By: jimmyz80
Date Posted: 26 Aug 2017 at 12:30pm
Originally posted by DavidBunin DavidBunin wrote:

How is the MLB wired to your IFD540?  Is it through the serial data interface, or is it through the ARINC 429 interface?  What is your IFD configuration for data ports?

I'd have to go double check but I do know that when I had the IFDs updated to 10.2, they made sure the connection on both ends was in compliance with the service bulletin relating to setting the protocol correctly.  I believe that was for the RS232 connection between the devices.


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2006 Cirrus SR22 - IFD540 IFD440 DFC90 AXP322 MLB100



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