View Full Version : Answer to the APRS ?

Seldom Seen
02-26-2008, 01:05 AM
The digital mode for sending position data on 2 meter is AX25. AX25 protocol uses 1200 baud Bell 202 audio frequency-shift keying(AFSK) I apologize, it's not phase shift keying

02-26-2008, 01:46 AM
Did I understand correctly, form the discussion in class, that in order for APRS to function the rig needs to have a GPS unit connected up to it? That makes perfect sense of course as obviously the rig needs to know where it is at in order to report its position.

I have neither a GPS unit nor a HAM rig yet but am weighing my options. I like the benefit of the APRS for various reasons, just want to make sure I understand what else is needed to make it really work :thumb:

Seldom Seen
02-26-2008, 02:17 AM
Yes you need a GPS, a TNC (terminal node controller) and a radio. The GPS sends your location data to the TNC, the TNC encodes it and sends it over the air to a digipeater. A digipeater is a repeater that is connected to the Internet and is able to receive the digital signal and send it to a site like find-u.com or UIview.com. The location of the transmitting station shows up on a map.

APRS can also be done simplex where the TNC is connected to a computers sound card and the data is decoded and overlaid on mapping software.

Some radios can be purchased with a built in TNC so all you have to do is connect a GPS. Icom now has a rig with a built in TNC and GPS.

02-26-2008, 08:28 AM
Thanks for the answer Seldom Seen. Ax25 and AFSK make perfect sense. BTW-the message sent from the GPS to the TNC is a NMEA-0183 GGA message. This is the autonomous location of the GPS receiver and should be accurate to about 6-10 meters CEP. There are many other message types that could be used including velocity and timing.

You can read about NMEA here: http://www.nmea.org/pub/0183/

and Here: http://www.nmea.org/pub/0183/

02-26-2008, 08:59 AM
So I get this ham radio thingie, see, and I do it because I want to talk to people further away from me than, like, a CB can reach, see? So I hears about this class, it will help me get a license so I can talk, and I works out a dealio so's I can get a radio without royally ticking off my :Princess:, right? So I am pretty much set to talk on this dang thing soon's as I figger out all those dang buttons, which I figger Dave will teach me about.

I figger some time I will get the time and ability to install the dang thing in between doing everything else...

Then I keep hearing about all this techie stuff and I understand some of the words but the music escapes me... I ain't a gonna ever catch up to this stuff.

Will you still talk to me? :confused:

02-26-2008, 01:57 PM
Will you still talk to me? :confused:

We'll still talk to you...We just won't know where you are at :D

I'm with you Bill...LOTS of information to digest and now I understand why folks like UB state that passing the test is really only a small baby step into the HAM world. It seems safe to say that using a rig on a regular basis is what is really needed to "learn" about HAM, which is pretty much how everything in life works. You can buy a 4x4, read about using it, listen to folks that use them, but there is nothing like first hand experience to really teach you how to realize its full potential :hill: