VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Avionics / Interiors / Fiberglass > ADS-B
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #61  
Old 10-19-2018, 04:11 PM
TimO TimO is offline
 
Join Date: Feb 2005
Location: Wisconsin
Posts: 435
Default

Ah, sorry Rocketbob, with your reply I understand what you are saying. On the Lynx they implement coasting. Yes, I think basically all good systems implement coasting to one degree or another, because you're right, you can receive those broadcasts any time even from 2 people at the same time. Coasting absolutely helps get rid of disappearing. It's one of the things we did in our box to fix all that mess with the Echo. Sadly, it's just one of the many things that aren't done quite right. I'm not sure what qualifies as "the biggest" problem, but certainly one important one is also the lack of sorting, so you may pick up a target 50 miles away but not pick up one that's 1 mile away. But I won't go on and on anymore about it. I pulled mine out, stuck in the L3, and couldn't be happier. If people want to build the filter box, all the info is available, and they help a lot.
__________________
Tim Olson - CFI
RV-10 N104CD - Flying 2/2006 - 1375+ hours http://www.MyRV10.com
RV-14 N14YT - Flying 6/2016 - 290+ hours http://www.MyRV14.com
RV-10/14 Transition Training: http://www.RVCFI.com
Reply With Quote
  #62  
Old 10-19-2018, 04:22 PM
rocketbob's Avatar
rocketbob rocketbob is offline
 
Join Date: Jun 2006
Location: 8I3
Posts: 3,029
Default

From what I understand the Packet Error Rate (PER) on 978 is around 33%. So 33% of packets get stepped on, lost, whatever. The ground stations lose these packets and don't rebroadcast them, so they get dropped. Add shadowing, less than ideal antennas, etc. one can see how the system is flawed.

Coasting is the bandaid fix for these flaws.

No other countries have adopted the 978 standards, and this sort of thing tells me why.
__________________
Bob Japundza CFI A&PIA
N55BC RV-6 borrowed, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
Reply With Quote
  #63  
Old 10-20-2018, 08:00 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,111
Default

Quote:
Originally Posted by rocketbob View Post
From what I understand the Packet Error Rate (PER) on 978 is around 33%. So 33% of packets get stepped on, lost, whatever. The ground stations lose these packets and don't rebroadcast them, so they get dropped. Add shadowing, less than ideal antennas, etc. one can see how the system is flawed.

Coasting is the bandaid fix for these flaws.

No other countries have adopted the 978 standards, and this sort of thing tells me why.
In layman's terminology... are you saying uAvionix can't fix disappearing targets with software revision? When they say they're working on fix - you think it's technically not possible...
__________________
-
Jim Stricker
Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 406

LSRM-A Certificate 2016
Special Thanks to EJ Trucks
Reply With Quote
  #64  
Old 10-20-2018, 11:32 AM
330drvr 330drvr is offline
 
Join Date: Sep 2009
Location: Clearwater FL
Posts: 87
Default

I don't know the software ins and outs, but the Navworx install had no disappearing targets and it only received the 978 signal. Echo gets both 978 and 1090 traffic directly. I still am hopeful (maybe I am naive) that a software fix from Uavionix Echo is feasible.
__________________
Bruce Brock
N174MR
RV-7A
IO-360
Dual GRT HX & Mini
Dual Adaptive AHARS
GNS 480 Navigator
Dues paid 2018
Reply With Quote
  #65  
Old 10-20-2018, 01:29 PM
rocketbob's Avatar
rocketbob rocketbob is offline
 
Join Date: Jun 2006
Location: 8I3
Posts: 3,029
Default

Quote:
Originally Posted by Piper J3 View Post
In layman's terminology... are you saying uAvionix can't fix disappearing targets with software revision? When they say they're working on fix - you think it's technically not possible...
Most systems "fix" the problem by caching the targets for a period of time after the target disappears. Sometimes the target reappears and you don't notice the difference. They likely just need to tweak their software to cache closer targets longer. This is an educated guess.

Also what I am saying is that the ADS-B 978 protocol is poorly designed, so 978 units have to make up for technical deficiencies of the system. This is one of the reasons why no other countries have adopted the same system.
__________________
Bob Japundza CFI A&PIA
N55BC RV-6 borrowed, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.

Last edited by rocketbob : 10-20-2018 at 01:34 PM.
Reply With Quote
  #66  
Old 10-20-2018, 02:04 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 5,354
Default

Is this problem unique to UAT? e.g., there are more 1090 SES units out there than UATs. Do UATs run at lower speeds?
Reply With Quote
  #67  
Old 10-20-2018, 09:00 PM
TimO TimO is offline
 
Join Date: Feb 2005
Location: Wisconsin
Posts: 435
Default

I don't know the RF side of things with nearly as much detail as the serial side of things, but it seems to me that both 978mhz and 1090mhz would have the same basic transmissions, and it's something like once per second that they send their information. There's less bandwidth in the 1090mhz spectrum overall, but on the 978mhz side, they also send weather/notam information too. So in some respects I can see that taking a bit of that larger bandwidth up. Still, I am doubtful that the simple fact of sticking wx+traffic on the 978mhz side should cause any worse traffic issues than on the 1090mhz side. I think really that most everybody in Avionics does some coasting. And I think that on either side, that helps a lot. I know for sure when I was still running the echos, that adding traffic sorting and then coasting did some drastic improvements to the traffic functionality of the system. If you simply strip out the non-factor traffic, that drastically too would improve the serial data flow. So getting better function out of the system should not be THAT hard. We did it ourselves. What really got me to give up was the constant ghost/shadow targets that I simply could not get rid of. With NavWorx, it was a VERY VERY occasional thing. But that box had a lot stronger transmitter. I think the very much less powerful transmitter in these micro boxes probably adds to the shadow target problem because you have radar stations picking up your transponder from far far away, but the GBT may not "see" your UAT signal at the same time. That makes it much harder for the system to merge these targets. I was getting shadows all the time when flying around MSP airspace, doing flight profiles that were never a problem before. And, even with the new Lynx, are not a problem. I really got tired of hearing "traffic" only to see it located at my own position. I think we got that all figured out too, but after spending hundreds of hours and probably nearly $1000 extra dollars on stuff along the way, I felt it was best just to move on. There are just too many things that really should be improved, and transmitter power is one that I couldn't do anything with.
__________________
Tim Olson - CFI
RV-10 N104CD - Flying 2/2006 - 1375+ hours http://www.MyRV10.com
RV-14 N14YT - Flying 6/2016 - 290+ hours http://www.MyRV14.com
RV-10/14 Transition Training: http://www.RVCFI.com
Reply With Quote
  #68  
Old 10-21-2018, 03:46 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,111
Default

TimO

Would weak echo Tx power explain disappearing target as I explain in my post #56 above?
__________________
-
Jim Stricker
Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 406

LSRM-A Certificate 2016
Special Thanks to EJ Trucks
Reply With Quote
  #69  
Old 11-12-2018, 01:47 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,111
Default

I emailed Kurt at uAvionix again to ask if any progress on echoUAT disappearing targets. Ryan at uAvionix Support replied and sent a software “build” for me to try and report back.

Problem is I fly off of a grass field and this fall it is a total swamp with all the rain in the northeast. I may not fly again until spring.

I asked uAvionix if others could try and evaluate this new software. Ryan asks that each person wanting to try the software to contact him so he can control the release.

Email…. support@uavionix.zohodesk.com
Attn: Ryan

You can find the file update process here: http://uavionix.com/support/update-echouat-software/

Keep me in the loop...

Jim
__________________
-
Jim Stricker
Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 406

LSRM-A Certificate 2016
Special Thanks to EJ Trucks
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:34 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.