ACARS question

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ShiftyPotts

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Hello group,

I've got an SDR radio tuned to a ACARS frequency and have plotted about 10 planes in the past couple of hours using Multipsk and PlanePlotter.

Will I get more planes if I monitor more frequencies? Do different planes use different frequencies? I live in a rural area so I don't expect to see many planes.

Thanks,

Bob
 

SkiBob

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I am near the Atlanta Airport there are many that use 136.80 while Delta mainly uses 136.85. It may be different in other regions, but that's my experience. Leave it sit on a frequency for an hour and see what you find.

Depending on your set up, you can expect a range of about 250-300 miles when planes are at cruising altitude.

You might find more response in the aircraft data decoding forum. I would suggest that this gets moved there. Aircraft Data Decoding - The RadioReference.com Forums

Have fun discovering.
 

ShiftyPotts

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Thanks SkiBob,

Maybe SDR isn't the best tool for ACARS? Thanks for letting me know about the other forum. I hadn't come across it before.

Bob
 

ka3jjz

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I've moved the thread. Please note that the Utility forum is for frequencies below 30 Mhz

As to VHF ACARS - do you have your squelch wide open? There is a very short data burst before each transmission, and if you don't hear it, no decode. Not every receiver (or SDR) can open up fast enough

You can mute the speakers so you don't hear the noise all the time...Mike
 

ShiftyPotts

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As to VHF ACARS - do you have your squelch wide open? There is a very short data burst before each transmission, and if you don't hear it, no decode. Not every receiver (or SDR) can open up fast enough

You can mute the speakers so you don't hear the noise all the time...Mike
Thanks for moving the thread to the right forum.

I'm pretty happy with how the SDR (Elad FDM-S2) is working, not using squelch at all. I have a virtual audio cable from the SDR to Multipsk. In the past 5 hours I've got 127 downlink transmissions, 19 with location. I guess my question is: do you have to monitor all the ACARS freqs to get ALL the planes? If that's the case, then I guess an SDR isn't the best tool.

Thanks,

Bob
 

ka3jjz

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I can tell you from my perspective (I did this when I was living near Baltimore Washington Intl Airport) that some aircraft will indeed use other frequencies besides 136.85. Unfortunately that won't well with many radios for exactly the same reason as why you should keep the squelch off - it you don't happen to be on frequency when the sync data burst occurs, you won't get a decode. That applies to most scanners and likely some SDRs too. I'm sure there are a few scanners that open up fast enough when scanning - I'll let others chime in on that....

It's been too long for me, but you should check out the other freqs - I'm pretty certain 136.85 isn't used that heavily around here, but maybe in your area, that's different. There is a nationwide common, but I just don't remember it off the top of my head (131.55?)...Mike
 
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ATCTech

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131.550 is the primary frequency in North America for Rockwell Collins ARINC conventional ACARS service. If a particular location only has one ARINC frequency, that will be the one. At busier locatoins ARINC may deploy 3, 4 or even 5 frequencies. Data exchanges between the aircraft and gound station frequency hop as directed by the ground station network to optimize usage.

136.850 is the Primary (and as far as I know is STILL) the ONLY frequency in North America for Sitacom, ARINC's major competition. Most carriers will use one or the other, very few subscribe to both services as there's not a lot of the developed world left where one service operates and the other does not, especially when you take satellite services over terrestrial VHF onnections into account.

Last but not least is VDL-2 mode, which uses 136.975 pretty much universally. Think of it as "high speed ACARS", capable of much more data trasnfer in both directions over conventional old ACARS. Both R/C ARINC and Sitacom operate VDL-2 ground stations in North America.

Cheers!

Bob
 

Alacrity174

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ACARS Freqs

Hello group,

I've got an SDR radio tuned to a ACARS frequency and have plotted about 10 planes in the past couple of hours using Multipsk and PlanePlotter.

Will I get more planes if I monitor more frequencies? Do different planes use different frequencies? I live in a rural area so I don't expect to see many planes.

Thanks,

Bob
Hi Shifty

Where in the country are you, this would help some to ID the best freqs to monitor.

As has been said there are 2 ACARS providers in the US, SITA and ARINC, think of them like AT&T and Verizon each airline can chose which provider to use so you will never catch all aircraft on a single frequency. There are also multiple frequencies in use at each airport, especially the busy ones. The ACARS providers use base frequencies, Terminal frequencies, En-route frequencies and also the Common Signalling Channel for VDLM2 which is 136.975Mhz, this will be changing soon as FAA NextGen is implemented. Also remember some airlines encrypt their ACARS transmissions (DLH is a prime example). You shouldn't have any problems receiving transmissions, the ARINC standard ramp up time is 85ms so as long as your scanner is running open you should catch the data burst.

ARINC uses the below as main base frequencies across the US
129.40
129.35
130.20
129.85
130.8
129.45 (JFK)
129.35 (LGA)
131.725
131.55

SITA uses
136.85
136.65
136.575
130.875
128.975

Hope this helps.
 

ShiftyPotts

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Yes, thanks. This is very good information. I live in western South Dakota (Black Hills), not near a big airport, so I don't expect to get lots of planes. But in just a few hours yesterday, about 20 planes popped up in my DXView map through Multipsk. I thought that was pretty good :) I was on 131.550 with an SDR receiver.

I'm kinda new to this (and SDR), so I'm just playing around in the different modes, trying to see what I can learn. I want to be able to identify more digital modes when I see them in the waterfall.

Now, I've come across the Mode S Beast. That might be kinda interesting!

Bob
 
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