ACARS Decoding. Troubles? Frustrated!

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hackinstack

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Sep 29, 2008
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I have an Icom R20 tuned to 131.550mhz, open squelch, AM mode. I have an audio cable from the R20 to a PC running Airnav (demo). Airnav shows the signal strength in the bottom right around 50% but I get *NO* data. I am on the approach path to O'hare and can literally watch the planes coming in overhead. (guess-timating they are below 5000ft)

Anybody have any ideas on what I'm missing? I've tried everything and can't understand why this is not working....
 

terryr

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Nov 29, 2009
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Without the radio plugged into the PC are you able to hear data when it is transmitted?

I live about 2-3 miles from SFO and I don't get much traffic on 131.550 but see most of my traffic on 131.125 and more on 130.340. 131.550 here seems to be used mostly for General Aviation and International. I see Frontier, United, American, Alaska, US/America West on 131.125.

I experienced the same problem as you initially. Listen for data and if it is distinguishable enough (strong enough) from the static to decode. Listen to the output on your PC to see if it's clean... I had a minor ground loop hum which prevented any messages from being decoded. Try other frequencies as well during peak times. Out here there may be several minutes that pass between transmissions.

I have an acarsd server running on 131.125 which is listed in the acarsd server list. Connect to it and you should have a good idea of the timing between messages and what they should look like.
 

hackinstack

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Terry -- Thanks for the feedback. I tried a couple different things and finally got it working. I'm not sure now *what* exactly it was that I fixed, but I was able to get data. I think it may have had to do with the mini-din cable I was using from the radio to the PC. Although it was hooked up it may have had the connector wiring backwards...

I ended up capturing close to 40 transmissions in just a couple hours. And oddly enough, I got *better* reception with the stock antenna on the R20 than I did with my Radio Shack discone... (which normally picks up everything better)
 

terryr

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Glad everything is working for you!

Now run acarsd and setup a server for us to connect to :D
 
D

DaveNF2G

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Good luck with acarsd if you switch. It cannot plot to a map correctly, although it does just about everything else it is supposed to do. Data formats are not documented accurately in the docs or on the user screens for the program, either. The latest wide beta (version 1.70RC3) uses an incompatible data format so information accumulated with earlier versions must be rearranged - in some mysterious way because again it's not documented properly - before the latest version can read it.
 

terryr

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Nov 29, 2009
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Good luck with acarsd if you switch. It cannot plot to a map correctly, although it does just about everything else it is supposed to do. Data formats are not documented accurately in the docs or on the user screens for the program, either. The latest wide beta (version 1.70RC3) uses an incompatible data format so information accumulated with earlier versions must be rearranged - in some mysterious way because again it's not documented properly - before the latest version can read it.
I totally agree with you. I run the Airnav ACARS Decoder along with acarsd. Airnav seems to decode more messages with interesting content. acarsd does a good job of decoding most of the tracking data and has an interesting database. Knowing how many contacts I've had with an aircraft is pretty interesting.

I use the Airnav Suite to tracking flights from both ACARS sources and PC HFDL. I think it does a great job and you don't have to create your own map.

At this point I primarily run acarsd so others can connect and get data along with correlating data with my other decoders on other machines. As far as I know there is no server capability with the Airnav products.
 

pilotman1260

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Oct 12, 2005
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There will be with the new one that is coming out,they sent me an e-mail yesterday,even though i don't own one yet,the 2010 version has several upgrades including data and a server capability.
 

apd3190

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Apr 9, 2004
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270
Location
Maryland
Just dowloaded nav air acars and im getting the same random numbers and letters as i did with freeware. i thought this decoded to readable text?
 

semo

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Jul 29, 2005
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North Dunklin County, Missouri
Acarsd has the ability to use the checksum method to see if the data is correct. Airnav and wacars does not, any decoded data will show even if it is incorrect. This is why Airnav has more decodes, but it also has more unreadable/ incorrect messages. If you do not receive a good signal Airnav will often show an unreadable message.

Also, acars messages normally requires some knowledge about what they contain.
For instance from my acarsd log:

ACARS mode: 2 Aircraft reg: .N662AA
Message label: H1 Block id: 8 Msg. no: D024
Flight id: AA9434
Message content:-
#DFBA3M5240602STL DFW N38190W0905732657M420342038G0009N38171W090596275

6M435327031G0009N38152W0910182908M455307038G0009N38134W0910403064M497

300046G0009N38116W0910613199M505310048G0009A1405
-----------------------------------------------------------[28/12/2009 00:02]

The above shows an American Airlines Flight 9434 enroute from St. Louis to Dallas Fort Worth. The message content contains the GPS coordinates North (N)and West (W) along the route.
 
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