2M Packet Go-Box
The goal of this project is to have a self contained go-box for 2m packet communication. The first goal is APRS RX/TX as there is the most software support available, with Winlink, SSTV, and TCP/IP over AX.25 as future goals.
The box consists of a 2m radio, a small computer, a small router/access point, a GPS dongle, and a 12v to 5v DC/DC converter. The only necessary external connections are 13.8V DC power and a suitable antenna. The goal is to have the box controlled by a wireless device like a phone, tablet, or laptop that remotely connects over WiFi.
For the radio I am using a Vertex VX-4000V. I bought the radio a few years back for packet use and it is perfect for this application. The radio has a DB25 connector on the packet making it easy to hook up a TNC or soundcard to the radio. The radio can do 50W or 25W and draws 12A on TX @50W. It is definitely not the lightest or most efficient radio out there, but it is built like a brick and works well for this application. I picked up a mounting bracket for the radio to make it easier to mount to the case. I used 3M VHB tape to attach the mounting bracket to a piece of aluminum square tube which was then epoxied into the case. This was so the radio would be high enough to access in the case.
For initial testing I used the same USB sound card I had already built, with more information here. To fit everything cleanly I need a soundcard without the TRS connectors, as they make it too long to fit. I also cannot use the DB25 breakout board as it is too long.
Computer / Router
For the computer, I used a Dell Wyse 3040 thin client computer. These are similar in price to a raspberry pi and are easier to obtain right now. The model I have has a 4 core processor with 2Gb of RAM. Powerful this is not. When connected to a monitor the experience is slow and laggy, but luckily a GUI will not be needed. The computer takes 5V over a barrel connector. I picked up a cheap GPS dongle off amazon to allow real time position tracking.
For the router I went with a Mikrotik hAP lite. This has 4x 100Mbit ethernet ports and 2.4GHz WiFi. Speed is not a concern so the slow ports are not an issue. The router takes 5V DC over a micro USB port.
For running APRS I am using Dire Wolf as a software TNC. Dire Wolf can directly run PTT over the CM108 soundcard and send location using a GPS dongle. Other applications can connect over serial, TCP/IP, and other methods.
I am also using Polaric Server to map APRS signals. This server connects to Dire Wolf over TCP and allows other devices on the network to connect to a web interface to access an interactive map. When connected to the interest the server can also pull data from APRS-IS and act as an I-Gate.
Initially I hoped to be able to fit a 120VAC to 12VDC power supply in the box, but there wasn't enough room. A fused cable with Powerpoles comes into the box to a distribution block, where one cable runs to the radio, and another to a DC/DC converter to make 5V for the computer and router. I went with a Meanwell RDS-30G-5. This can supply 6A @ 5V with a wide input of 9V to 36V. With the radio transmitting at full power, and the computer and router drawing their max power, a 200W ,13.8V supply is needed. This is about 15A.