Getting into APRS recieving

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AronDouglas

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With my recent excitement of viewing and hearing the ISS flyover a week ago, I am noticing all the APRS traffic is my area as well as from the ISS when it flies over. And now I'm thinking I'd like to monitor some APRS frequencies. I am not a licensed amateur radio user, I just want to listen to whats out there.

With that said, is there and suggestion on what I might need to decode APRS signals? I know I need a decent scanner and a decoder. I'm watching a BCD996 for sale for $180 and that will be my new home base station, but what about decoders? I want a decoding software for my computer because I plan on controlling the 996 via my computer. Is there anything else I need? Is there a decoding software that stands above the crowd?
 

LtDoc

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It shoulodn't take much to get you started. You need a receiver that can hear 144.390 Mhz in FM, and a decent (tall) antenna. Some sort of TNC to interface your computer and receiver. Then software that will display the received information on the computer.
I can't say which is best, but I can tell you what I use. I have an old hand scanner that can be put on 144.390 Mhz in the 2 meter ham band. An audio cable from the speaker jack on that scanner that goes to the computer's sound card. I use a program called 'AGW Packet Engine' that acts as a TNC by using the sound card. Then a program called 'APRSIS32' that does the displaying on the screen. The only cost was for the audio cable, I already had the scanner. The two programs are free. It's not a simple 'plug-n-play' thingy, you have to follow the instructions. It's not that difficult though. There are user groups on Yahoo that cover both the AGW and APRSIS32 software, read them and ask questions.
Have fun.
- 'Doc
 

AK9R

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Any VHF receiver that can tune 144.390 MHz FM will do. You don't need an expensive scanner.

The hardware approach to decoding AX.25 packet (APRS is a subset of AX.25 packet) is to use a Terminal Node Controller (TNC). A TNC listens to the audio coming from the receiver, decodes the audio into zeros and ones, assembles those zeros and ones into packets according to the AX.25 protocol, and makes those packets available at a serial port which your computer can read. You can buy a general purpose TNC such as the Kantronics KPC3, or an APRS specific TNC such as the Argent Data Tracker3 or Byonics TinyTrak 3 or 4. Neither of these hardware TNCs have any ability to control your radio except maybe to turn it on and off.

Or, you can go the software TNC route with the AGW Packet Engine. This is a "sound card TNC" which performs the TNC functions using the sound card in your computer to decode the audio from your receiver. For more information about setting up a sound card TNC, see Introduction - Sound Card Packet. Note that these sound card TNCs won't control your radio, either.
 

BJ_NORTON

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Any radio that has a headphone jack and can tune 144.390 will work. I have a cord plugged into the headphone jack on my radio, and the other end is in the mic in jack on my laptop. I use Dire Wolf as a soundcard TNC and then let YAAC connect to it and see the stations moving on the map. It took all of 5 minutes to get it going, and it works perfectly!.
 

AronDouglas

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Thanks guys, this is sounding as easy as it looks. I've just been really busy these past few days so this project got pushed back a bit.

BJ, you said you hooked yours up to your laptop and used its sound card. Do I need a dedicated sound card to make this work or do I have to use integrated sound (I have a desktop rig)? I have literally dozens of sound cards, cheap ones and expensive ones in my parts closet. I assume any old card should work fine.

Thanks again for the help guys. I plan on making a dedicated antenna for APRS (cant have too many antennas :) ), so I'll add that to my list of rapidly growing radio projects :)
 

AK9R

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Do I need a dedicated sound card to make this work or do I have to use integrated sound (I have a desktop rig)?
No. You can use pretty much any sound card that the operating system and the sound card packet engine will recognize.
 

Jay911

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I have AGW Packet Engine running on my PC listening to the line-in port on my one and only sound card. Attached to that port is a BC796D scanner parked on 144.390 with the speaker out connected to the line-in on the sound card, so the scanner speaker is effectively "muted". The playback of the line-in port on the PC is also muted, so I also don't hear the squawks coming thru my PC. The only thing hearing the noises is the AGWPE software, and I can use the rest of my PC for everyday use. My sound card also has the ability to split inputs, so the front mic-in jack could be used for other purposes like videoconferencing or a temporary scanner feed (like I did last weekend) without that sound being corrupted with APRS packet noise.

Finally, AGWPE is feeding into APRSIS32 which is feeding all its data to the APRS-IS network. You can see it by checking aprs.fi for station VE6SRT. Admittedly traffic is quite low as I have just a back-of-set antenna on the scanner (the main purpose of my setup is to catch my own signals near the house, as digipeaters and other igates in the area don't cover my home location).
 

BJ_NORTON

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Any sound card will work fine. My understanding is that AGW packet engine has almost become a standard, and that dire wolf and other programs output their data in this standard. Dire wolf will decode APRS on its own and put them on screen in a readable format. Also it can be configured a a digi without any software. There was a post on the APRS SIG that suggested dire wolf has some error correction abilities that a standard TNC or TNC software don't have. APRS is a connection free system-there are no provisions to ask for a garbled packet to be re-sent - so any help getting packets decoded error free is something you want.

Anyway, going recieve only should be very simple-good luck!
 

fratermus

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OP: you can probably get a scanner that will receive that freq for $5 at a garage sale. Last one I picked up was $2.

If you can't source a cheap one locally I'll ship you one of my 10-ch programmable RS ones. You'll have to drag up a wall wart for it. The freebie will hold you over until you get something better. PM me if you need it.
 

AronDouglas

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OP: you can probably get a scanner that will receive that freq for $5 at a garage sale. Last one I picked up was $2.

If you can't source a cheap one locally I'll ship you one of my 10-ch programmable RS ones. You'll have to drag up a wall wart for it. The freebie will hold you over until you get something better. PM me if you need it.
Thanks fratemus, the offer is much appreciated but I have a scanner in mind already. My little BC72KLT should suffice since I'll have a dedicated tower mounted 144.39mhz antenna.
 

AronDouglas

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Okay, I finally got around to this project again. I went and got DiriWolf and I hooked my BC72XLT to my computers front mic. I'll throw a sound card in later, but for now I just wanted to play around with things. I'm also using Audacity (a free voice recorder) as a visual monitoring system so I can see whats going on. I have noticed that DiriWolf does not catch every packet (it misses 2 out of every 20 thereabout, but that could be from the poor reception and the scanner being indoors with a duck for an antenna). And just using basic deductive reasoning I understand 80% of what is being displayed (concordances, call signs, some text messages, ext)

I've learned so much just in the hour I've been playing with this thing. For instance, I now know where a local digipeater is located and where a few weather stations are just my googling the lat and long. Now I need to go get either YAAC or APRSISC so I can map everything.

From what I've read, I need to be a yahoo group member and a licensed Ham operator to get APRSISC, is this true? Or is all that required for people who want to use the APRS network through APRSISC? All I want is to listen and plot locations on maps, (as of right now) I dont plan on using the APRS network to transmits anything.

And just for fun, here is a few pics of the traffic I'm seeing from my local repeater at 12:00am ish. This was recorded over a 40+ minute time span.




All those lines look like this up close.
 

BJ_NORTON

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you don't have to be a mamber to download APRSISCE. download it here on the wiki page and you're all set. There is a flashing bar about getting you're passcode, and you only need that if you're a licensed ham trying to send what your station hears to the internet
 
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