ACARS Packets

[N467RX]

Well, I'm getting a lot of ACARS packets, but all are bad, what could be a possible cause of this? a faulty scanner-computer connection? the antenna? the squelch?

 

[datainmotion]

Typically the squelch on your reciever needs to be off/open to receive the sync signal needed by the software to decode the transmissions.

 

[N467RX]

It's completely open

 

[datainmotion]

Are you listening to the audio? Does it sound normal (if you are used to the sound of ACARS :lol: )? Do you hear any interference?

What software are you using?

 

[N467RX]

Multimode for OSX.

I'm using a PRO-99, what I don't know is if it tunes to AM by default, and if it does, how can I tune it.

 

[datainmotion]

I don't see anything in the info I viewed online for the Pro-99 indicating that the mode is selectable. Therefore, I think it would be safe to assume that it selects AM by default for the Civ Aero band.

However, according to the manual for the Pro-99 (http://www.scancat.com/OnLineHelp/OEM_Radiwners_Manuals/PRO-99_OwnersManual_20-515.pdf)
there is a Power Save feature on that unit that is automatically selected anytime you select a specific channel. This feature allows the scanner to "sleep" whil waiting for activity. I wonder if its not "waking up" quick enough to catch the sync signal?

You may want to post your question to the Radio Shack board here at RR (http://radioreference.com/forums/forumdisplay.php?f=81) and see if they can help.

 

[N467RX]

With the squelch set to off, the radio doesn't go to sleep, but I'm going to try while checking that.

 

[datainmotion]

I'm not sure if I would interperet that as "powers off totally" or just "powers down receiver".

 

[kicktd]

Well if you're getting packets and most of them are bad like that and everything is fine on your scanner then I would have to assume it's the program. I don't think anyone here has really used multimode for OSX.

I know ACARSD does a great job of decoding the packets and the only time I would get bad ones is if I left my squelch on by accident. Not sure if there is a way for you to run a virtual PC program or to put together a cheap PC to run ACARSD on but if you can get something running Linux or Windows check out ACARSD

 

[DPD1]

Multimode for OSX.

I tried it on a 780 and same thing... Nothing but bad packets. Though I heard quite a few that sounded plenty clear enough to me. Maybe try emailing Chris at Black Cat and see what he says. I'd be interested to hear if he has a solution. It might be something simple.

Dave
http://www.dpdproductions.com
- Custom Scanner, Aviation, MURS, GMRS, Marine & Ham Antennas -

 

[N467RX]

I'm going to try with a Windows computer and a different program.

 

[WhtRabit]

Also keep an eye on what applications you're running on the computer. Software decoding of any kind of packet data is very timing dependent. I had a 2.8GHz Pentium D with a Gig of ram that was having a hard time with software decoding 1200 Baud AX25 ham packet radio. As soon as I killed one particular application that was active in the background, I started getting almost perfect decoding.

Yes, this is a Windows example, but the idea applies to OSX or Linux too. If you're going to run something timing dependent like packet decoding, make sure your processor is as idle as it can be.

 

[kicktd]

I've run processor consuming processes with ACARSD running in the background and it would decode them fine even though I was using lots of memory and CPU time elseware. Guess it just depends from computer to computer and from what I understand ACARSD uses the sound buffers to decode so even though it might be slower decoding, it would still work.

AMD Athlon 64 3000+ and 1 gig of ram.

 

[WhtRabit]

Ya I'm in agreement with you kicktd, it is dependant on hardware, software, receiver, antenna, cabling, and various other factors. I'm just suggesting that processing resources are another variable to play with. One that hadn't been mentioned previously.

 

[kicktd]

True, wasn't disagreeing with you there as it does make a difference

 

[ka3jjz]

I didn't see anything as to whether you were trying to run on a laptop or a desktop - but even Mac laptops are probably prone to this. Laptop inputs are generally set up for low level applications - so pumping in earphone data may well be overdriving the inputs. That is another thing that can be critical when decoding using soundcard software - too much input and all you'll get is garbage.

If you are running Multimode on a laptop, you can either try an attenuating patchcord (RS had them, last I looked) or make one yourself with a cable and a 10k 1/8w resistor(or thereabouts) to drop the level. Also listen on a clear freq and see if all you hear is white noise- if you get some hash from the laptop, that will also cause problems. 73s Mike

 

[N467RX]

It's a lap, a Macbook pro.

I'm going to look for an attenuating patchcord. In the meantime, will a lower volume help me?

 

[DaveNF2G]

I made a comment on a similar topic in the thread titled "Acars problem."

 

[kicktd]

It's a lap, a Macbook pro.

I'm going to look for an attenuating patchcord. In the meantime, will a lower volume help me?

It very well could. I've noticed if I have the volume too loud it won't decode properly sometimes.

 

[datainmotion]

WACARS was like that as well...volume needed to be set to an agreeable level for the software. Also, if no one else mentioned it, make sure to check your audio settings if you are using the mic input - some machines have a 20dB gain feature that, if enabled will cause problems for the software.