Successful ACARS decoding?

[KA2ZEY]

I've been trying to get SDR Sharp and Plane Plotter working to decode ACARS. I tune to one of the designated ACARS frequencies (ex. 130.55 AM) and wait for the squawks. I live in NYC so there is a lot of airtraffic. The signals are routed via VAC to Plane Plotter. I tick the ACARS selection in I/O. I see that there is a signal but no data appears even though I can hear the ACARS sigs. And yes, SDR Sharp is output to Line 1. Does the ACARS signal have to be very, very strong? It's there but not super strong. Is there something I'm missing?

 

[ka3jjz]

Yes - if there is a squelch option, turn it off. Make sure you hear background noise when there's no signal. There's a 10ms (I think that's right) data burst that precedes each transmission. If the decoder doesn't hear it, you won't get any decodes

It's quite possible that the squelch isn't opening up fast enough. Many (though not all) scanners have this same issue...Mike

 

[KA2ZEY]

Yeah I've made sure the squelch is off. Filter audio is off. All of the usual suspects. Maybe the signal isn't strong enough which is weird given that I'm right under the LGA flight path and using a scanner antenna that I have wired into my RTL device.

 

[Markb]

ACARS doesn't require raw discriminator audio, so I would try adding the filter back in and adjust the filter width (8 kHz ?) and order. I would get the audio to a place where it sounds "normal" on a voice frequency and then switch back to the ACARS channel and pipe it to PlanePlotter.

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[ka3jjz]

Would you need to use Virtual Audio Cable (or similar) to get the audio to PlanePlotter? If it's not aware of the SDR, no matter what you do, it won't 'hear' the audio since it doesn't know it exists....Mike

 

[KA2ZEY]

Yes I'm using Virtual Audio Cable. I have PP set to 'Line 1' and SDR Sharp is out to 'Line 1'.

 

[BM82557]

For ACARS I use SDRSharp, VB-Audio cable software & the ACARSD decoding software. I never got good decodes for UniTrunker & DSDPlus using Virtual Audio Cable so I switched to VB-Audio a long time ago.

 

[Markb]

Yes I'm using Virtual Audio Cable. I have PP set to 'Line 1' and SDR Sharp is out to 'Line 1'.

I don't believe that PlanePlotter has the option to select your input device. Have you tried setting 'line 1" as your default recording device in Windows?

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[jazzbassNick]

In PP, I think the config is in Options/Audio/ACARS/Source. Not in front of it ATM. What do you have that set to?

 

[KA2ZEY]

Line 1 (VAC). And let me reiterate, I do see audio coming in on the signal page in PP.

 

[Your_account]

and you have to select "AM". I try acarsd but plane plotter work much better!
the huge problem is only possible to revice one channel at the time.

 

[jazzbassNick]

I saw that he said he had it on AM.

I'm running it now - SDR#>VBCable>PP. It's wired to my discone and it's getting occasional messages (on 130.45 & 131.55), not nearly as many as when I had it hooked up to a my homebrew coax-T.

Maybe it is just a question of reception.

 

[Your_account]

I get from my local Ham Radio Store an Antenna for that band. The price was ~50€ or mybe a little more.
Thats amazing what i cam receive now.. Where is only one problem i could not finde any splitter for the Signal.

 

[KA2ZEY]

Ah ok, so I came home and tried again. I found a very strong ACARS sig on SDR Sharp and PP decoded it although I don't see it on the map yet (the aircraft). Seems like you have to have a really good sig.

 

[Markb]

Did that particular message contain any position information? Most ACARS messages don't.

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[KA2ZEY]

Oh and I checked Filter Audio. Would that have something to do with it?

 

[KA2ZEY]

And if I use Google Earth with PP and click on one of the aircraft, it takes me off the coast of Africa. Something must be wrong with the calibration.

 

[Markb]

Perfectly normal behavior. Notice the lat/lon where those aircraft are located: 0° by 0°. Any ACARS aircraft (and possibly mode-s) with no position info will go to this location.
When you receive an ACARS broadcast with a valid lat/lon, it will plot in your part of the world.

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[KA2ZEY]

Ah ok, so it seems to be rarity that I'll get lat/lon data.

 

[Markb]

Yes. Definitely less frequent than ADSB hits. You may see a handful over the course of a day.

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