Setting up a Remote Station – Part 2 System Design and Components

Part 1 of this series covered the motivation behind this project and the requirements I set. This part will outline the system design and the components I’ve chosen.

System Design

Design Philosophy

The objective is to create a self-contained and secure environment that delivers the required functionality, looks after itself as much as possible, reports its status back to base and is fully remotely controlled. The desired location for the remote station is somewhere that already has Internet access and has a Wireless LAN that we can connect to. This avoids the need to rely on 4G access, but this will also be provided as a failover option.

I’ve chosen to deliver this using readily available components and base the control system on Home Assistant. Home Assistant is open-source software that can be used to monitor and automate just about all aspects of your home. It has a vast catalogue of supported devices and services and I’ve been using it for some years to add some smarts to my home.

I’m running Home Assistant on a Raspberry Pi 4 housed in the Argon One metal enclosure from Argon 40 with its companion M2 SSD to improve performance and reliability. I can’t speak highly enough for this enclosure. Not only is beautiful to look at, it has significant passive cooling plus a variable-speed fan. Having the SSD significantly improves the usability of the Pi – especially with the M2 SSD.

The Remote Station

  • Router with 4G modem and ability to join a host WiFi (if one is available)
  • UPS
  • Remote controlled mains switches for the Windows PC (if needed), and the Radio Power Supply
  • Raspberry Pi computer running Debian 11 (not Raspbian) and Home Assistant
  • Flex 6400 HF radio
  • Remote On/Off control system for Flex

The Home Station

  • Windows PC running SmartSDR
  • Microphone
  • Key
  • Other ham-related software such as VarAC

Component selection

Router

I’ve chosen to use the Teltonika RUT951 industrial router. I already have one of these installed in my motorhome and it’s excellent. It isn’t cheap, but it is perfect for this job. It delivers:

  • 4G dual MIMO WAN access with support for two SIM cards,
  • Ability to connect to an external Wireless LAN as a WAN
  • Automatic failover between the various WAN connections
  • Internal Wired and Wireless LANs with 3 physical ports
  • VLAN capability (not used in this project)
  • Digital I/O, Modbus support and MQTT
  • VPN server and client
  • Remote management (not used)

UPS

I’m not looking to power the radio for any great time in the absence of mains power, but I do want to be able to shutdown in an orderly fashion. I’ve opted for the APC BackUPS 650. This provides 650VA capacity, six protected outlets, plus two surge-protected only outlets.

The following devices are connected:

  • 5V 3A PSU for the Raspberry Pi Station Control Computer (SCC)
  • 9V 1A PSU for RUT951 Router
  • Tapo P110 remote controlled sockets for the Radio PSU and optional Windows computer
  • Raspberry Pi Station Control Computer running Home Assistant

I have a lot of experience with the Pi and with Home Assistant, so this combination was a natural choice. I’ll cover the Home Assistant configuration in another post.

Radio PSU

To give me the potential to maybe operate off-grid, I’ve chosen the MyDel PS-1335 12V 30AMP PSU with battery backup capability to give a 30A UPS. The MyDEL is an unknown quantity to me. It has a good spec and is supposed to have very low noise. We’ll have to see. Just in case it proves to be unsuitable for any reason, I have another 30A PSU I can use instead.

Flex-6400 Radio

Originally, I intended using my Elecraft K3S in the remote station and using something like RemoteHams to control it. After playing with RemoteHams, I felt that there was something missing. Also, there is the issue of power control on the K3S. You can remotely command the radio to power off, but you can’t power it on remotely. This needs to be done by toggling a control pin – not a problem, but an added complexity.

For a while now, I’ve been looking at the FlexRadio range, and realised that the 6400 is ideal for this application: after all, it’s designed to be operated remotely. I went for the straight 6400 rather than the 6400M. The one I have does not have an ATU. If the proof of concept works, I’ll add the ATU module.

I’ll cover the software and the detail of controlling the power to the 6400 in a separate post.

Author: Gareth Howell

IT Professional, radio amateur, scout leader and beer drinker. I enjoy helping small business use their limited IT budgets to best effect