Abstract
This project is a collection of former (and some +new) projects connected together to make an APRS digipeater, which +doubles as an APRS weather station, with PE1RXF telemetry server +capabilities.
+ +The story
+For several years I operate an APRS iGate on both 2 meter and 70 cm +LoRa. I added my own PE1RXF telemetry support (see: https://www.meezenest.nl/mees-elektronica/aprs_telemetry.html). +This worked fine, but I already had designed an updated version of the +iGate. The prototype worked, but had some issues. So I kept using the +old iGate and forgot all about the new version.
+Some time ago I started to design a weather station (https://www.meezenest.nl/mees-elektronica/weather_station.html) +which I located in the back garden. Because it was out of reach of my +wifi network, I used the APRS iGate prototype to send the weather data +via its build in LoRa modem to my PE1RXF telemetry server.
+Than the idea of relocating my existing iGate to the location of my +weather station emerged. The weather station had all the hardware I +needed build in. And it made sense to combine the two systems, as both +handle APRS traffic. Besides, both systems use energy so shutting one +down seems sensible.
+But the reason I used the APRS iGate prototype in the first place, +namely the absence of wifi, became a problem again. An APRS iGate has to +have access to the internet, that’s the whole point! But the amount of +data it sends is small, so I didn’t need lots of bandwidth. And at that +point another dormant project woke up: I always wanted to experiment +with TCP/IP over the air. In the past I did some experiments with TCP/IP +over AX.25 (packet radio), but the 1200 baud modems were simply too +slow. I also had build a 5GHz HamNet link, but 350 Mbit/s is quite the +overkill. I needed a link speed between 15kB/s to 500kB/s. The Rnode +project from https://unsigned.io/hardware/RNode.html +seemed perfect.
+The design
+Weather station
+This project started with a weather station. I designed it as a stand +alone weather station with an RS-484 ModBus interface. It can measure +wind speed, wind direction, rain fall, humidity, air pressure and +temperature. The complete build document of the weather station can be +found here: https://www.meezenest.nl/mees-elektronica/projects/weather_station/build_doc/weather_station.html
+ +Brains
+Although stand alone in operation, to read the measurements the +weather station must be connected to a host via RS-485. This host is a +Raspberry Pi LoRa shield I designed to be the successor of my first APRS +iGate. It is a simple PCB with room for a Raspberry Pi Zero 2 W, a LoRa +transceiver, a real time clock and a power supply.
+ + + +Peripherals
+The Raspberry Pi need some extra hardware for interfacing the various +peripherals, like the transceiver, the ModBus and the Rnode modem.
+USB hub
+As the Raspberry Pi only has one USB port, a hub is essential. I used +an old one I had laying around. Taken out of its case, it fits +perfectly.
+RS-485 dongle
+To interface with the weather station a USB to RS-485 dongle is +needed. A cheap one from Joy-IT (https://joy-it.net/en/products/SBC-TTL-RS485) +is fine.
+ +1200 baud APRS modem
+This modem I also had laying around. It is called “Packet modem nano +2” and it is based on the Micromodem from unsigned.io (https://unsigned.io/hardware/MicroModem.html). +The design files for this modem are part of this project and can be +found in the git repository.
+ + + +Rnode modem
+For the low speed network link I use the Rnode project from https://unsigned.io/hardware/RNode.html. +This is an amazing project and I only use a small part of the features +available. In my ow project is works as a KISS compatible LoRa modem. +Together with the tncattach program (https://unsigned.io/software/tncattach.html) +it forms a Linux network adapter over which I can route all the network +traffic. The maximum speed is just above 20 KB/s, which is enough for +APRS-IS traffic. For archival reasons, I included the source code of +tncattach as well as rns (the firmware and configuration utility) in the +git repository.
+The hardware on which the Rnode firmware is flashed is a LilyGO +LoRa32 v2.1 (also known as TTGO T3 v1.6.1). Of course you need at least +two boards to form a network. With a good antenna, the range is easily +100 meters (and probably more than 1 km), which is plenty enough for +what I need.
+ +More than brains alone
+The Raspberry Pi with all the extra hardware is housed in a small +plastic housing. On the back panel behind the SMA connectors and the +power jack, I placed a copper strip. This acts as the start grounding +strip on which all other ground wires are connected. This prevents a lot +of RF and EMC problems.
+ + + +External hardware
+2 meter transceiver
+The 2 meter transceiver is an old Alinco DJ-580 hand held radio with +an output power of 5 Watt. It is connected to both the 5 pin DIN +connector and the 12 Volt barrel jack on the Raspberry Pi.
+ +Diplexer
+The LoRa APRS transceiver (70cm) and the APRS transceiver (2m) are +connected to a triplexer, making it possible to use one dual band +antenna for both radios. Why a triplexer? Well, I had one laying around. +I terminated the unused 1200MHz connector with a 50 Ohm load. But a +diplexer would have been sufficient, of course.
+ +Antenna
+This is a simple 2m/70cm dual band antenna from Diamond, the X30.
+ +The build
+Software
+The instalation of all the needed software on the Raspberry Pi is +complicated, so I wrote a separate document: installation_pe1rxf_aprs_weather_server.html
+The specifications
+-
+
- 2 meter transceiver with 5 Watt output power +
- 70 cm LoRa transceiver with 20 dBm output power +
- Raspberry Pi Zero 2 W +
- APRS cross band digipeater software +
- Weather station via ModBus +
- Rnode TCP/IP over 70 cm LoRa for internet +
License
+Copyright (C) 2023, 2024 M.T. Konstapel
+ +The software is published as open-source software (GPL). The hardware +is published as open-source hardware (OSH).
+Software
+This program is free software: you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by the +Free Software Foundation, either version 3 of the License, or (at your +option) any later version.
+Hardware and documentation
+This work is licensed under a Creative Commons Attribution-ShareAlike +4.0 International License.
++