APRS – Making it work

Konrad_Roeder · 2018-05-10T12:56:59.209Z

We really can’t send a LoRa signal to the ISS. LoRa is 1.6 MHz wide. But, an old-school Kantronics TNC with a 2M radio can send a short message back at 1200 Baud. It can do the trick. Before someone (drug addict?) stole my Kenwood TM-710, I was able to regularly send packet data at 1200 baud through the ISS.

I will eventually get Direwolf running on a Raspberry Pi that has a UDRC hat. It can drive a Baofeng. It’s essentially a 1200 and 9600 baud packet modem. This is my (on hold) portable ISS terminal project using Direwolf w/RPi The old school 1200 and 9600 data needs to be abandoned. We need to move far beyond where I was 30 years ago, wire-wrapping a Z80 running Forth, etc.

Enter DreamCatcher running LoRaWAN or chat. Yes. I’m waiting for my DreamCatcher 3.03 for this reason. At one end, there would be an iGate-like connection into the APRS network over the Internet or into a wide-area high speed packet network here in the Seattle Area called HamWAN HamWAN is OFDM on 5.9 GHz. It’s very much line of sight. Although it’s good with multipath, it can’t penetrate foliage, make it through buildings, etc. It has a high PAPR and zero process gain. LoRaWAN could extend that network. Yes, the 433 and 915 MHz bands are an option, but these are both very crowded and unfortunately don’t allow any enforcement of the boundary between ham radio and the shared ISM bands. This is why I’m so interested in getting DreamCatcher transceiving on the 1240-1300 MHz band. It’s the Beyond Line of Sight high-speed data solution for hams.

Eventually there will be LEO satellites carrying LoRa store and forward for those places where 20-30 miles on the ground is not enough. But maybe in the future there’s a LEO Cubesat that is on a band that can repeat/relay a LoRa signal, we would have a high-speed connection for maybe a half of a dozen packets because that connection would be shared.
We have some really nice bands on 1.2 GHz, 3.3 GHz that could be carried aboard. Ideally, that satellite would carry a store and forward mechanism in it. It saves the data it got from the remote location and then dumps it when the LoRa ground station is in view. LoRa is very Doppler immune, ideal for the application.

–Konrad, WA4OSH

clavo · 2018-05-10T18:28:23.137Z

Any idea how to get the DC to beep? Maybe play a wave file / ringtone?

Again the goal goes back to have it alert me when a message comes in that matches at filter I set.

APRS Pager of sorts…

-liam

Konrad_Roeder · 2018-05-10T19:04:50.849Z

Liam,
The program to actually parse the data at first is going to live outside of the DC in a laptop. It will have to wake-up on a periodic basis and read the JSON file, parse through it for your callsign, etc. When one is found, it will need to create a notification. Your laptop will know how to deal with the notification. Next, it will have to know somehow that it’s already seen all of the messages up to some time. This is where that missing time stamp comes in.

I think I’m going to write this app in Node-RED so that we have access other facilities in the laptop. The language was invented by IBM and it’s portable across all sorts of platforms. In fact, it could live inside of the DreamCatcher once they see what can be done with it.

I have already installed it on my Linux laptop. If you are on a Windows platform and want to try it out: Windows Install. You can also run it on a Mac, Raspberry Pi, etc.

You will see what I’m up to. I think we’ll be able to build all sorts of applications to query the DreamCatcher with it and extend its capabilities. The key is to have good, working APIs that make building the applications much easier.

–Konrad, WA4OSH

clavo · 2018-05-10T20:45:13.559Z

I installed it. Feel free to share code! Thanks for working on this.

-liam

Konrad_Roeder · 2018-05-11T00:10:10.129Z

OK … now if you can go to 127.0.0.1:1880 and get it up and running, watch a couple of introductory videos on YouTube. It’s a really easy language to learn. You pick the elements you want to run and connect the dots. You will see the large library of elements you can use for inputs and outputs.

–Konrad, WA4OSH

Konrad_Roeder · 2018-05-11T01:55:02.253Z

OK … I can query the DreamCatcher’s APRS API with Node-RED code. Now, I need to figure out how to parse out the call signs out of the text.

Screenshot from 2018-05-10 18-48-16.png1278×695 126 KB

The first node is essentially a button that starts the process.
The next node makes the HTTP call to the API which returns a JSON data structure
The JSON node takes the JSON data structure and extracts the text.
The msg.payload dumps the output of the JSON node into the debug window, which you can see on the right.

On the left is a palette full of Node-RED functions that can be used to process the data.

–Konrad, WA4OSH

ac8dg · 2018-05-11T02:18:35.188Z

I’m not great at the network stuff.

Can two devices connect to the dreamcatcher at the same time? For example on my wifi network, can one computer run skylark ui and a second computer interrogate the dreamcatcher with the getAPRS ?

Konrad_Roeder · 2018-05-11T02:26:24.647Z

Yes. You can browse what’s on your dreamcatcher on one window and make queries on another window.

Here’s my DreamCatcher through the web interface you are familiar with

Screenshot from 2018-05-10 19-20-52.png1276×696 795 KB

Here’s a command line querying my DreamCatcher

Screenshot from 2018-05-10 19-22-46.png1279×698 571 KB

and … developing Node-RED code in yet another session that is also querying my DreamCatcher.

Screenshot from 2018-05-10 19-24-00.png1278×695 85.8 KB

Cool, eh?

–Konrad, WA4OSH

Konrad_Roeder · 2018-05-11T03:23:52.863Z

I answered your question for multiple sessions in one computer as yes.
The answer for multiple computers looking at the DreamCatcher at the same time is also yes.

One DreamCatcher can serve maybe a 5-15 people using laptops or tablets over Wi-Fi.

–Konrad, WA4OSH

Konrad_Roeder · 2018-05-11T04:47:24.549Z

Screenshot from 2018-05-10 21-21-01

Screenshot from 2018-05-10 21-23-54

Note that the most recent message is on top, but I don’t have any idea when it was sent.

Screenshot from 2018-05-10 21-28-46.png745×68 16.5 KB

Note that KE7WWT’s messages are malformed. The OUTNET “callsign” is not padded on the right with spaces as required by the standard. Outernet should probably not forward mal-formed APRS messages.

Screenshot from 2018-05-10 21-44-40.png819×633 87.6 KB

OK here’s my NodeRED script … it parses through the JSON data structure looking for the : which is the beginning of the TO call sign. I still have some work to do. But it’s almost impossible to know if I’ve seen a message already without a date-time code included in the JSON record.

Screenshot from 2018-05-10 21-31-08.png1262×612 77.9 KB

–Konrad, WA4OSH

clavo · 2018-05-12T05:40:14.176Z

Question. Not sure if this has been answered before… but for a message to get picked up and sent through Outernet, does the word ‘outernet’ need to be capitalized? Thx.

–liam

Abhishek · 2018-05-12T07:20:55.332Z

“OUTNET” and yes, needs to be in all-caps.

Edit: by request, “outnet” (all smalls) works too, now.

kb2sdrjay · 2018-05-12T10:47:17.615Z

Perhaps that should be added to the user manual?

kenbarbi · 2018-05-12T11:17:17.422Z

Konrad is going to work on a separate Apps Manual, and should add it. Ken

Konrad_Roeder · 2018-05-12T13:43:19.248Z

I will definitely will be working on the Apps Manual. APRS is definitely a section that I’m going to cover.

–Konrad, WA4OSH

ac8dg · 2018-05-12T23:27:23.833Z

While “one-way” transmissions are not really allowed… I have proved you can send an aprs message to callsign OUTNET and if picked up and sent into the aprsis system it will be captured and re-transmitted.

But I should follow the rules and at least send it to ourselves as a “valid callisign”

Sending to OUTNET is probably the “extreme” of third party traffic

aprs to outnet.PNG1158×619 625 KB

Konrad_Roeder · 2018-05-13T01:21:18.693Z

Jim,
First of all, APRS is a one-way transmission. It falls under telemetry in FCC part 97.

This is well known and it’s part of the standard. Look in section 4 Destination Addresses.
OUTNET padded with three blanks is a valid destination in APRS. There are actually quite a few like those.

This station is actually using OUTNET as a source call sign:

Screenshot at 2018-05-12 18-09-20727×45 5.19 KB

And, the APRS system accepted the message. It shows the source is in Corvallis, OR.

But Outernet should not be accepting malformed packets. Everything in red is malformed:

https://aprs.fi/?c=raw&call=KE7WWT*&limit=50&view=normal

Screenshot at 2018-05-12 18-20-181009×345 91.7 KB

References:
FCC Part 97 Regulations
APRS Standard

–Konrad, WA4OSH

Konrad_Roeder · 2018-05-13T15:48:02.960Z

Using the existing API, which returns the 50 or so most recent APRS messages, without any idea when they were sent, we can get the 5000 character-long “result”, split it into individual messages (looking for the \n), and then stuff everything into a workable JSON structure using a parser. Then the applications can look at the elements in the data structure and do various things like notify the user that an APRS message came it, flash lights, forward the packet to some other network (Twitter or Email could be examples), etc.

Here’s what the Node-RED flow will look like for an APRS twitter bot.

OuternetAPRSTwitterBot.png748×410 34.1 KB

There’s still a couple of issues.

We need time stamps to know when the messages were received. Do you want to act on old messages or act more than once? A stitch in time saves nine.
We need to find a parser that will accommodate both uncompressed and Mic-E formats and is known to be pretty error free.
The current API can only return a fixed number of records.

It sure would be nice if a real API was provided that returned a useful JSON structure instead of this pathetic mess of a giant character string without time stamps.

–Konrad, WA4OSH

Konrad_Roeder · 2018-05-13T16:00:47.983Z

Here is an APRS parser written in JavaScript that might just do the trick:
npm-aprs-parser

I will see what it will take to wrap it inside of a Node-RED node.

–Konrad, WA4OSH

ac8dg · 2018-05-13T16:19:33.587Z

Konrad_Roeder:

do various things like notify the user that an APRS message

Could this be ported to a arduino feather or esp32

adafruit.com

Adafruit WICED WiFi Feather - STM32F205 with Cypress WICED WiFi

Discontinued - you can grab Adafruit HUZZAH32 – ESP32 Feather Board instead! Say "Hi!" to the WICED Feather! Perfect for your next Internet connected project, ...

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or the email alert thing I use
https://www.pixeltwenty.com/espalert.html

I don’t see outernet changing the standalone-robust sklyark OS, but a second cheap board w/wifi could do a lot.turning on lights, sms or email.