APRS Digipeating and Path Selection 101

[sdnative]

Hector:

Smith suggests the following string for use in "rural" areas:

WIDE1-1, WIDE2-2 (Will produce three hops and will take advantage of home fill-in digis. Use in rural areas with low APRS activity only.)

With most systems ignoring wide3-3 or treating it as a single hop, this suggestion seems to be a legitimate means to get an extra hop or two. Would this idea have improved our ability to get messages out of the Parashant back to LA?

And, would this be a legitimate way to get "extended" range from the APRS system?

Wide3-3 should be avoided as you are broadcasting indiscriminately in all directions for quite possibly hundreds of miles. Remember, APRS is meant for local tactical operation. If you need to communicate long range (SD to LA for instance) it is probably better to define the path from here to there instead of increasing the number of broadcast hops (which is what you are doing with WideN-n).

It is analogous to the internet. Can you imagine what would happen if the internet backbone was comprised of hubs (which broadcast all traffic to all ports indiscriminately) instead of using routers/switches (which have very specific routing tables)? The internet would cease to function due to the sheer amount of traffic/ packet collisions). The same applies to RF transmissions / routing. Am I wrong here?

[cruiserlarry]

So, again, what would be the best path to use for local LA communications? WIDE1,1, WIDE2,2 ?

And how do we define more specific paths for longer distance tracking / messaging without using "indiscriminate hops"? (Sounds like ingredients in a cheap beer )

[DaveK]

So, again, what would be the best path to use for local LA communications? WIDE1,1, WIDE2,2 ?

And how do we define more specific paths for longer distance tracking / messaging without using "indiscriminate hops"? (Sounds like ingredients in a cheap beer )

Larry:

Among the many things that get discovered in this maze of APRS is that success depends on a lot of black magic. The short answer to your question is that in the greater LA area you can probably get away with less than wide2-2. If you are communicating over longer distances, wide2-2 will help.

For you, communicating with Hector, Frank or myself, wide2-2 might be more than is necessary. Getting to Ollie in San Diego, wide2-2 would be indicated. So much depends on the digipeaters that serve both stations, the terrain that separates you, how busy the system is, the black magic in place at the time of transmission....................... Get that rig up and running and lets sort you out.

[sdnative]

Among the many things that get discovered in this maze of APRS is that success depends on a lot of black magic. The short answer to your question is that in the greater LA area you can probably get away with less than wide2-2. If you are communicating over longer distances, wide2-2 will help.

For you, communicating with Hector, Frank or myself, wide2-2 might be more than is necessary. Getting to Ollie in San Diego, wide2-2 would be indicated. So much depends on the digipeaters that serve both stations, the terrain that separates you, how busy the system is, the black magic in place at the time of transmission....................... Get that rig up and running and lets sort you out.

I guess my point is that WideN-n should be used for local operation or to get to an Igate or when a path is unknown. Communications over any distance would not use the WideN-n paradigm at all (except Wide1-1 which is just a RELAY). You would specify the major digipeaters manually. Here is a post from Ollie:

One other question. When Dave and I were within say 50 miles of one another I was able to see him on my GPS and send him messages. Outside of that we couldn't do anything. At least I couldn't anyway. I believe he got my messages and could see me but I din't get his messages nor could I see him. Maybe my path is wrong???? Let me run something by you and see if my understanding is correct... If using the example in the image below if I were to input a path of "Wide2-2, K6NEX-1, K6NEX-5" that would plot my signal path to the LA area from San Diego providing those K6NEX-? stations were relay staions????

In this example he used a series of K6NEX-* digipeaters to reach LA. I am not sure the Wide2-2 was necessary, a Wide1-1 may have been better. So his path may be something like "Wide1-1, K6NEX-1, K6NEX-5"

Relevant info from the original post:

Because all APRS digipeaters use the same generic call signs, the re-transmission process can happen in several geographic directions simultaneously if several more digipeaters are within range of the one transmitting. A widening circle of digipeats involving more and more digis on each hop will spread outward from the user in all directions. This phenomenon, known as UI flooding, is sharply different from the directed linear sequence of digis, each identified by a unique call sign, used in traditional connected packet.

If you know them, you CAN use explicit call signs in APRS paths instead of the generic WIDE. This is one approach to reducing unnecessary retransmissions, especially in your home territory where you likely will know the actual call signs of local digis.

This is the way I understand it, please correct me if I am missing something.

[cruiserlarry]

My rig has been up and running for some time...I track you, Ollie, and Hector all the time, but don't get responses to my messages (of course, I am assuming your near the unit when you have APRS running).

I guess what was my primary confusion is has been explained clearer now; WIDEn,N is a generic path when none is known, while you can specify a chain of digipeaters if you know where they are and their call signs. I believe UI-View 32 has lists of digipeaters based on your current location, so I could input a path string based on the location of the recipient for my message - is that correct?

[OLLIE]

My rig has been up and running for some time...I track you, Ollie, and Hector all the time, but don't get responses to my messages (of course, I am assuming your near the unit when you have APRS running).

I guess what was my primary confusion is has been explained clearer now; WIDEn,N is a generic path when none is known, while you can specify a chain of digipeaters if you know where they are and their call signs. I believe UI-View 32 has lists of digipeaters based on your current location, so I could input a path string based on the location of the recipient for my message - is that correct?

I'm pretty sure you are correct Larry. If you can find a path down to me then if I could reverse that path we could message each other.

I know I can email you from my radio now. I was messing with tat the other day. Quite fun actually. Here's how it work.

Under Call Sign type: EMAIL
In the text type: (email address) (text)

Example:
Call Sign: EMAIL
TEXT: john.doe@hotmail,com I'm on my way home.

The APRS IS digipeater recognizes that you want to send an email due to the call sign entered and searches the beginning of the text for an email address format. It then sends the remainder of the text after the email address as the email body text.

[DaveK]

My rig has been up and running for some time...I track you, Ollie, and Hector all the time, but don't get responses to my messages (of course, I am assuming your near the unit when you have APRS running).

I guess what was my primary confusion is has been explained clearer now; WIDEn,N is a generic path when none is known, while you can specify a chain of digipeaters if you know where they are and their call signs. I believe UI-View 32 has lists of digipeaters based on your current location, so I could input a path string based on the location of the recipient for my message - is that correct?

Larry:

Using arps.fi for your call sign (either w6lpb or w6lpb-1, 7,9, 12), it shows that you have not been on the system since April 14, 2009, over 3 months ago. While you may be able to view the system, you don't seem to have transmitted any positioning information since 4/14/09.

If you are not connected to the system, this may explain why you are not able to send messages. If you give me a call, I will activate my APRS and see if we can do the message thing.

As an aside on the path question, it will tend to make more sense as you experiment with different paths to different locations. Sometimes it is a matter of good guess work to select the mountain tops which you think have the greatest likelihood of success reaching the intended recipient of your message. Other times you can log onto sites like aprs.fi and place your cursor over your position or others who have successfully contacted you to get the digis that were used.

[cruiserlarry]

DaveK -

I have been on APRS since that time, virtually daily. I have had other radios see my position. Even at our board meetings in Torrance, Ollie was able to see me, so I know the signal has been active all this time. I don't understand why arps.fi doesn't see me when other users have in different areas. So, we'll have to check it out next time we get together...

[sdnative]

I can see him:

http://aprs.fi/?call=W6LPB&mt=m&z=11&timerange=3600

For some reason on my computer the website only shown his position icon when using Internet Explorer. When using Firefox, the map centers on the same location, but no icon is shown.

I presume that is his shop.

[DaveK]

DaveK -

I have been on APRS since that time, virtually daily. I have had other radios see my position. Even at our board meetings in Torrance, Ollie was able to see me, so I know the signal has been active all this time. I don't understand why arps.fi doesn't see me when other users have in different areas. So, we'll have to check it out next time we get together...

Larry:

Our last board meeting was in March.