[aprssig] APRS Newbie - Overwhelmed

[Curt, WE7U]

On Sun, 21 Jan 2018, Michael Barnes wrote:

> I am wanting to get into APRS and am rapidly getting overwhelmed. My intent
> is to have APRS in my vehicle to see stations around me and to allow my
> home station to track me. I have a Raspberry Pi with touchscreen and TNC-Pi
> connected to a Kenwood HT with external antenna for the truck. That station
> will run Xastir. Most of the home monitoring I am assuming can be done with
> a computer displaying aprs.fi.

If you haven't yet, join the Xastir email list at xastir.org (near the bottom of the main page). Myself and others will help you with Xastir questions there.


> I guess the first thing I am looking for is an APRS for Dummies guide to
> help me get started. I'll need to figure out how to configure the mobile
> for reporting or beaconing or whatever it does.

At one point there existed some very nice intro material. One of the more knowledgeable users posted it years ago. If you look back in the archives or do a search through the mailing list by other means you may find it. I can't recall the author now but perhaps someone on here can point you to it.

There's the APRS spec:

     www.aprs.org/doc/APRS101.PDF

And two addendums if you want to figure out how everything kind'a works, but the intro material I mentioned above is more your speed. The spec is dry reading if you're just getting started. It's quite useful to those of us that implement parts of it though.


> I'm also trying to make sense of aprs.fi. I see a ton of icons on the map,
> but I have no idea what they all are. I am especially confused by a large
> number of what seem to be non-ham entities on there. I am seeing fire
> lookout towers, tug boats and Navy ships, what looks to be home weather
> stations, aircraft, and others. Some of these show different identification
> than ham callsigns, including aircraft numbers, marine and commercial
> callsigns, and some kind of weather identifiers.

You can get much of that with Xastir too if you try hard enough! The ships come in from the AIS system. Airplanes from ADS-B. Weather stations can be from ham stations or from the citizen's weather stations.

In Xastir you can also receive AIS and ADS-B, using cheap RTL-SDR dongles and a few small programs running to inject that data into Xastir via UDP packets. Of course in those instances you're only receiving the ships and planes you can directly receive over RF.


> From what I can gather, APRS depends on a lot of digipeaters to receive
> data from mobile units and both relay that info to other users as well as
> upload the data to the aprs.fi system, presumably via the Internet. I'm
> trying to figure out how all that aspect functions as well.

Yea. There are digipeaters and there are igates. Two separate functions, although both functions can be in one station. Some mobile & portable stations can also function as digipeaters. There are also ways of running cell-phone programs to get on the internet side of APRS (inject packets into APRS-IS directly instead of over RF). To use a cell-phone with APRS on RF you'd need a transceiver hooked to your phone, which a very few people do.

Igates can gate in one direction or in both directions between the APRS-IS (APRS internet system) and ham frequencies and only gate APRS protocol packets through. Bi-directional igates allow messaging between any two APRS stations anywhere in the world. One-direction igates only gate APRS packets into the APRS-IS and are not useful for messaging.


> Following the digipeater info is, what about areas out of range of a digi?

In that case you may be transmitting into the void and have nobody pick up your transmissions. You can go to high-power on VHF to try to get in, you can go to HF transmissions to be heard, or you can put your own digi's up to cover areas that are otherwise uncovered.


> What are the procedures for putting a digi in place?

You'd need to get familiar with your local area and talk to the movers and shakers of APRS there. Some areas have APRS coordinators that can help you figure such things out. My area is one of those (WA state).


> Do folks have portable
> digis that can be deployed temporarily to serve a non-covered area for a
> specific event or emergency?

Yes. It's not that hard.


> Do all digis have to be connected to the
> Internet?

No. Only igates.

Have fun!

-- 
Curt, WE7U.        http://we7u.wetnet.net
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