Best SDR# settings for ACARS? Bandwidth?

[Joe91]

I've had very poor results trying PDW (despite success with POCSAG paging) so I'll give ACARSD a try after reading a helpful thread here.

But I'm puzzled what exactly should be the settings for SDR# (RTL dongle). Looking at the waterfall zoomed in, it seems to use a fair old chunk of a 25kHz channel. Nothing I've found online yet tells us the actual bandwidth. Do I set it to include the full width of the modulation on the waterfall? I assume the Filter Audio setting needs to be OFF? What about the AGC settings that appear in AM mode?

I hear loads and loads of bursts of data at varying strengths, and only once in a 'blue moon' do I get anything decoding in PDW, and even then with plenty of errors. How fussy are the volume levels - does it have to be incredibly precise?

Thanks

 

[DaveNF2G]

Pick a strong burst and then drag the filter edges to match its bandwidth.

 

[Yokoshibu]

Dave is right, I recommend you turn on the squelch and adjust it 2 clicks above where it just begins to burble / or chop in and out. I run 3 instances of SDRSharp into virtual audio cable and then feed that into plane plotter. I used to run 4 radios into acarsd with the option to process multiple inputs selected... I don't see why you would have any problem... also acarsd at least provides you a numerical readout on the volume setting as long as the number isnt over 2 digits in length you should be good!

 

[Joe91]

Thanks. I had originally seen RTL-SDR Tutorial: Receiving Airplane Data with ACARS - rtl-sdr.com which says "6KHz works best for me" but if people have been using conventional scanners designed to work on 25kHz spaced channels where various ground station offsets may be in use... it can't be all that critical so long as nothing creeps in from adjacent channels.

I was just wondering - out of curiosity - if anyone knew what the actual technical spec says in terms of bandwidth, if anyone has a link to such a thing.

That page also says "turn OFF AGC, and set the filter order to the lowest setting of 10." which I question too. If I turn OFF the AGC the audio volume varies all over the place - at least with AGC it ends up fairly consistent. And the page also says "Acarsd is a free decoding program, however we find its decoding performance to be vastly inferior when compared to PlanePlotter." so it seems that I'm probably on a hiding to nothing trying to get any sense out of ACARS for free?!

 

[DaveNF2G]

I have had exactly the opposite experience vis-a-vis PlanePlotter and other ACARS programs. PP is consistently the worst performer for me.

 

[gariac]

I have had exactly the opposite experience vis-a-vis PlanePlotter and other ACARS programs. PP is consistently the worst performer for me.

Ditto this. Acarsd is very good. [I've given up on PP. Too buggy.] The problem is rtlsdr isn't a particularly good radio at VHF frequencies. They are fun to play with. I have half a dozen, though I never ran more than 4 at a time on one computer. But in the VHF band, they are really junk. The best thing you can do with one is decode mode-s. For that purpose, they are as good as a "real" receiver.

The good news is you can use just about any old scanner for acards. You don't need a demod tap, but it sure helps. Something like a pro-2035 gets $50 tops on Craigslist.

 

[DaveNF2G]

The discriminator tap should do absolutely nothing for AM reception. The purpose of the discriminator is to help demodulate FM.