Getting started in APRS

[K7XRL]

Ronald, APRSdroid doesn't need a radio, it periodically blurts your position out over the phone's data connection. Then you see it over the APRS-IS and can view it on sites like aprs.fi. It's pretty cool and dovetails nicely with over-the-air APRS.

My PM inbox here is full and I need to archive/empty it out, but I'd be happy to help you set it up off-line (or ask you how you're setting up that Bluetooth link to the radio, that would be new for me). Let me know and I can set something up or maybe take it to its own thread.

Thanks for your offer!

I tried sending a pm but I guess it is still full. What I really want to learn is how to specify a path, and how to program filters for specific packets.

 

[AK9R]

We have a forum for such questions and there are several folks on here who are very familiar with APRS.

Ask away!

As for APRS paths, keep in mind that APRS is based on using un-connected packets in an environment where the digipeaters use aliases so that the user doesn't need to know the exact names of the digipeaters in the area. If I set up my digipeater to digipeat on the alias "WIDE1" and I see a packet from you with "WIDE1-1" in the path, my digipeater knows that you are asking it (and every other WIDE1 digi that can hear your station) to digipeat your packet. In doing so, my digipeater changes your path to "WIDE1" which the digipeaters interpret as "WIDE1-0" which means don't bother digipeating this packet.

So, to take advantage of the local network, a mobile APRS station is encouraged to transmit using the path "WIDE1-1,WIDE2-1". Your packet will be digipeated back out as "WIDE1,WIDE2-1" which means that only WIDE2 digipeaters will act on it for the second hop.

There's a pretty good explanation of APRS paths on this page:

APRS Paths And Digipeating 101

Skip down to the discussion of the "New Paradigm" and don't forget to click the link to the animated GIF.

 

[K7XRL]

Ok thank you!

So basically, without using aliases I would need to know the call sign of each digipeater I wanted to retransmit my packets, is that correct?

That clears up quite bit

So the next question is how do I configure filters for incoming packets? I saw a page yesterday that had all of the potential filter options, but I am not sure how to string them together to get the effects I might want.

Realistically I probably will only use a radius to ignore packets that aren't within a certain range, but I want to understand how to use the other filters in case I want to use them some day.

Thanks again,

Ron

 

[K7XRL]

After doing more searching and reading, I found this link, which seems to have a good description of paths.

APRS Paths And Digipeating 101

If I understand correctly, a WIDE1-1, WIDE2-1 path is designed to hit small home based "fill-in" digipeaters with the alias WIDE1 and wide area mountain top or club repeaters with the WIDE2 alias, (which will also act upon the WIDE1 alias so your packets don't get lost if a home digi doesn't hear them). Is this correct?

So WIDE1 = home "fill-in" digipeaters

WIDE2 = big wide area repeaters


What type of stations use the WIDE3 alias?

 

[AK9R]

The link you posted is the exact same one I posted in the second message in this thread.

The filters you are talking about primarily apply to the data your computer receives while connected to the APRS-IS. A complete list of filter commands can be found here: Server-side Filter Commands

Some APRS devices, such as the Kenwood and Yaesu APRS radios have some APRS filtering built-in. You'll have to refer to their respective manuals for instructions.

WIDE3 is rarely used. Many APRS digipeaters won't even respond to a WIDE3. The whole idea behind the WIDEn-N paradigm is to limit the number of hops that your packet makes. The APRS RF bandwidth is limited and excessive hops reduces everyone's access to the network.

 

[K7XRL]

The link you posted is the exact same one I posted in the second message in this thread.

The filters you are talking about primarily apply to the data your computer receives while connected to the APRS-IS. A complete list of filter commands can be found here: Server-side Filter Commands

Some APRS devices, such as the Kenwood and Yaesu APRS radios have some APRS filtering built-in. You'll have to refer to their respective manuals for instructions.

WIDE3 is rarely used. Many APRS digipeaters won't even respond to a WIDE3. The whole idea behind the WIDEn-N paradigm is to limit the number of hops that your packet makes. The APRS RF bandwidth is limited and excessive hops reduces everyone's access to the network.

So it is! I must have overlooked how I arrived there. In any case, it was the right place for the best explanation, so thanks!

I will be using the APRSdroid android app on a phone and/or tablet. I know it allows you to use filters. The app itself has a link to a web page that describes the various filters and what they do, but I am a little unsure of how to string them together to get the desired effect. In other words, I know that I can set a filter to receive only weather, for example. But I don't know how to set up a filter to receive weather, objects, and mobile stations within 3 separate zones on a map (though I believe this is possible).

So if the filters are intended to filter only packets coming from APRS-IS, does that mean packets received via RF will not be filtered at all?

I don't have any pressing need to do so, I just want to understand the system better.

 

[AK9R]

The packets in the APRS-IS were injected directly using a device connected to the Internet. Those packets may have originated via RF and were injected by an I-Gate. When another device comes along and accesses the APRS-IS, whatever filtering is applied by that device will apply to all packets handled by the APRS-IS.

Here are some examples:

If you use a range filter, let's say "r/33/-97/200", you will see all packets in the APRS-IS that are within 200 km of latitude 33 N and longitude 97 W.

The my range filter, "m/200", would show you all packets within 200 km of your last reported position. Note that if you never send a position report, the my range filter will yield nothing.

If you use a type filter, let's say "t/w", you will see all packets of type Weather. You can add to the type filter by saying, for example "t/tw", and you will see all packets of type Telemetry .OR. type Weather.

You can also use filters to reject packets. A filter of "-t/w" would show you all packets except those of type Weather.

Multiple filters separated by spaces in the same filter command act like an .AND. statement. For example, "r/33/-97/200 t/w" would show you all Weather type packets within 200 km of latitude 33 N and longitude 97 W.

 

[K7XRL]

Ok, that makes sense. I will give it a go and see if I can make filters work. Thanks for all of your help!