</p><p>This work is licensed under a <arel="license"href="http://creativecommons.org/licenses/by-sa/4.0/">Creative Commons Attribution-ShareAlike 4.0 International License</a>.
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.
This project is a collection of former (and some new) projects brought together to make an APRS digipeater, which doubles as an APRS weather station, with PE1RXF telemetry server capabilities.
---
@ -45,9 +45,13 @@ Although stand alone in operation, to read the measurements the weather station
[PDF version of schematic](./images/RPi-LoRa-shield_schematic.pdf)
To make this board work for this build, all the power button stuff has to go. That is all the transistors and the surrounding resistors, capacitors and diodes. And the 555 timer must also be removed. The RTC should be mounted on the bottom of the board instead of the top. After that, a Waveshare ethernet/USB hat is sandwiched between the pcb of the shield and the Raspberry Pi.
The Raspberry Pi need some extra hardware for interfacing the various peripherals, like the transceiver, the ModBus and the Rnode modem.
The Raspberry Pi needs some extra hardware for interfacing the various peripherals, like the transceiver, the ModBus and the Rnode modem.
### USB hub
@ -75,17 +79,9 @@ For the low speed network link I use the Rnode project from [https://unsigned.io
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.
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.
As a ham, I use the 433 MHz version, of course.
[Large version of photo](./images/raspberry_pi_proto.jpg)
@ -97,9 +93,29 @@ The 2 meter transceiver is an old Alinco DJ-580 hand held radio with an output p
### 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.
The LoRa APRS transceiver (70cm) and the APRS transceiver (2m) are connected to a diplexer, making it possible to use one dual band antenna for both radios. The diplexer is designed specially for this project. The port isolation is not great, but because of the small transmit power of the two transceivers, this is not a big deal. And even so: it outperforms a commercial Diamond triplexer on the 70cm band.
All the inductors are made from 1mm copper wire (preferably silver plated) and wind around a 6mm rod (a screw driver or a drill bit for example).
#### Adjustment procedure:
- Connect a dummy load to the combined 2m/70 cm port
- Connect an SWR meter and a 70cm transmitter to the 70cm port
- Adjust C1, C2 and C3 for the best SWR
- Connect the SWR meter and a 2 meter transmitter to the 2m port
- Adjust C4 and C5 for the best SWR
- Repeat the two steps, as both ports influence each other
[Large version of photo](./images/assembled_prototype.jpg)
## 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](./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
- 2 meter transceiver with 37dBm (5W) output power
- 70 cm LoRa transceiver with 20 dBm (100mW) output power
@ -78,7 +78,7 @@ When GPIO16 goes low (external button pressed), RPi goes into shutdown.
### Insert the SD card in the Raspberry Pi and press the power button
During the first boot, the Pi will reboot once. Because of the external power button, this will not work: the Pi will shutdown. Power up the Pi by pressing the external power button again.
During the first boot, the Pi will reboot once. Because of the external power button, this will not work: the Pi will shutdown. Power up the Pi by pressing the external power button again. (obsolete)
marcel
