Category: Digital Modes

Single Board Computers and Amateur Radio

Single Board Computers and Amateur Radio

Since the advent of the home computer there have been radio amateurs who have explored the possibilities of using computers in their shacks and as computer technology and software have developed it has allowed more amateurs to be able to use a computer in their shack even if it is just for logging and looking up call signs on QRZ.Com.

In recent years there has been a new kid on the block, the Single Board Computer or SBC which as the name suggests has all the necessary components required mounted on a single board whereas on a desk top computer the various components are attached to a central circuit board via cables.

There are a number of SBC’s available but the one that kicked off this change is the Raspberry Pi SBC, there is a lot of support out there for this SBC and over the past few years they have been featured more and more in articles in Amateur Radio magazines here in the UK and abroad where radio amateurs have used them in their radio related projects.

So what is the Raspberry Pi ?

First and foremost, the Raspberry Pi was a product that was produced to be a fairly cheap way for children to get involved in computing and programming either through education in schools or for use at home and in order to facilitate this further the cost of a Raspberry Pi has always tried to be around the £30 mark. Despite being made to what you might consider to be a tight budget the Raspberry Pi uses the best components available at that time.

Over the years there have been various models of the Raspberry Pi and currently the main model (most powerful) of the Pi is the Raspberry Pi model 3 B+ which can be purchased for around £32 to £34 depending upon where you buy it.

Since its release in 2012 the Raspberry Pi is one of the best-selling computers of all time (number 3 in the rankings according to a recent report that I read). Makers and hackers have since taken up its use in a big way and use it in all manner of smart tech projects and so have radio amateurs. Due to its cheap price several of these little computers can be used at once for various radio applications, consider if you ran two or three separate computers/laptops in your shack then the space required let alone the cost involved would be prohibitive for most people.

Specifications for the Raspberry Pi model 3 B+

  • Broadcom BCM2837B0, Cortex-A53 (ARMv8) 64-bit SoC @ 1.4GHz
  • 1GB LPDDR2 SDRAM
  • 4GHz and 5GHz IEEE 802.11.b/g/n/ac wireless LAN, Bluetooth 4.2, BLE
  • Gigabit Ethernet over USB 2.0 (maximum throughput 300 Mbps)
  • Extended 40-pin GPIO header
  • Full-size HDMI
  • 4 USB 2.0 ports
  • CSI camera port for connecting a Raspberry Pi camera
  • DSI display port for connecting a Raspberry Pi touchscreen display
  • 4-pole stereo output and composite video port
  • Micro SD port for loading your operating system and storing data
  • 5V/2.5A DC power input
  • Power-over-Ethernet (PoE) support (requires separate PoE HAT)

In order to use this single board computer (as with most SBC’s), you will need to connect it to a monitor via the HDMI connector, you will also need a keyboard and mouse, power is provided by the use of an old phone charger with a micro USB connector or an official Raspberry Pi power supply.

The Raspberry Pi does not come with an operating system loaded onto the board so in order to use it you have to load an operating system onto a micro SD card which then plugs into the appropriate Micro SD slot on the Pi. The Raspberry Pi website has various operating systems that are available to download and when it comes to using the computer for amateur radio purposes then fortunately there are amateurs out there who have written software for us to use.

Amateur Radio Uses for SBC’s

About three years ago I bought myself an SDRplay software defined radio. There are various software downloads available for the SDRplay which are supported by Windows, Mac, Linux etc. and one of the computers listed that is supported with compatible software is the Raspberry Pi. I initially used the SDRplay with a windows laptop, I had heard of the Raspberry Pi but at that time I didn’t know anything about them or what they were.

On club night in the spring of 2016 I was sitting next to a couple of members who were discussing creating a D-Star hotspot using a Raspberry Pi, I mentioned that my SDR radio could be operated using a Raspberry Pi, but I didn’t know anything about them. The upshot was that I was lent a Raspberry Pi 2 model B which I had a play around with at home, the only down side for me was that the connection to the internet was via an Ethernet cable and considering my shack is in the front upstairs bedroom and my internet router is downstairs this created a bit of a problem, I didn’t have an Ethernet cable that long and I didn’t really want to go down that path every time that I wanted to connect this computer to the internet.

Doing some research on the internet about the Raspberry Pi I saw that about a month or so earlier a raspberry Pi 3 model B had been released with an increased performance over the Pi 2 and it also had Bluetooth and Wi-Fi connectivity as standard. I decided to buy one but due to the improved connectivity of the new version of Pi it was selling out fast, so I had to trawl through a lot of sites before I found a trader who still had some in stock.

So now I had my own Raspberry Pi and I connected it to my mouse, keyboard and monitor. I found that it was just a computer but in a different form factor (Linux based) and there is quite a lot of software already loaded onto the board. There is software relating to programming and coding and a Libre Office package which (I think) is very similar to Microsoft Office and I now also use it on my Windows laptop.

I downloaded the software for the raspberry pi off the SDRplay website and loaded it onto a micro SD card, connected everything up and I was up and running without any problems at all.

Another SBC that I use is the Latte Panda which does utilise Windows 10 as its operating system and it is downloaded onto the board so basically any software that you would use on a laptop or base home computer can be downloaded onto this SBC.

Since my initial foray into connecting my SDRplay to a Raspberry Pi, I have set up another Pi as an ADSB receiver with a connected dongle which I have running 24/7.

I have also played around using the Raspberry Pi for decoding data modes, namely FT8.

I am continually looking at other amateur radio uses for the  SBC’s that I own and apart from the projects I have outlined they can be used in the following ways; As your main shack computer, for logging, as a WSPR transmitter, for tracking satellites, as a DV Hotspot, as an APRS gate, as a rotator controller or for decoding CW to name just a few applications.

For their cost and size these little computers are great fun to use and are a very cost-effective way of using a computer in the shack and going back to comments made at the beginning of this post I can potentially use four of these little computers at the same time for ham radio.

 

73’s Graham M0GAE

FT8 – The Basics

FT8 – The Basics

FT8.
It has been around for a while now and the protocol itself has undergone some radical changes recently so what’s all the fuss about, and is it actually worth bothering with?

Ham Radio digital modes are a bit like Marmite, you either love them or you hate them and FT8 is no exception to this rule, well that’s not strictly true because FT8 has come in for it’s fair share of stick over recent times due to it’s quick and dirty QSO method. Basically FT8 has a very stripped back QSO exchange that only actually comprises of CQ Call, a signal strength exchange and a confirmation.

FT8 was developed by Joe Taylor K1JT and amateurs typically use it as part of the WSJTX software package which can be downloaded from here

Here is a typical conversation over FT8:

“CQ G0SBN IO95”  CQ call from G0SBN
G0SBN 2E0EFP IO95” 2E0EFP replies with their location
2E0EFP G
0SBN +06” G0SBN responds with a signal report
G0SBN 2E0EFP R-02”
2E0EFP confirms signal report & replies with his own report
2E0EFP G0SBN RR73” G0SBN
 says Reception Report Received, Goodbye
G0SBN 2E0EFP 73” 
2E0EFP says Best regards

Each message of up to 13 characters takes 13 seconds to send. There are 4 slots per minute, and your transmission  block lasts for 15 seconds, then the software listens for any replies for 15 seconds, and so on. A typical exchange above takes around 90 seconds to complete. Great ! You’re thinking I can get loads of DX in a short window, and that is indeed a fact but it’s quite devoid of any user interaction. This is where some amateurs seem to have an issue because it’s basically M2M (Machine to Machine) transactions and can actually be automated so the operator needn’t even be in front of his radio / shack PC to stack up a load of QSO’s

Is that cheating ? You decide !

So I am guessing by now the burning question is how do I get into this brave new world and make some QSO’s ?

Now this isn’t going to be a full on guide on how to setup your radio for FT8 but I will share some details on some tips I have found during my setup etc. As a minimum you will need the following:

A shack PC, (WSJTX Can be ran on Windows, MAC OSX, Linux)
An audio interface from your shack PC to you radio
Optional CAT Control of radio from shack PC

As well the above you should check the following settings on the radio, AGC is off, Data mode is ON and the SSB mode is USB. Most FT8 or digital modes in general users normally say the ALC should not be invoked by the radio when transmitting.

Now there is a little bit of PC jiggery pokery required here to ensure your shack PC can hear the signals coming from your radio (via the mic input) and can also send the data signals to the radio via the speakers output. Withregards to the ALC invocation, I would normally set the sound card input level on the radio to a fairly low setting and then set the shack PC speaker volume manually when transmitting to make sure the ALC is not being triggered.

Similarly with the reception of signals, you don’t want the RF from the radio overloading and clipping the audio into the PC, so again check your Mic level on your sound card and monitor the received signal on WSJTX to ensure that the reception signal is around -60dbm.

Have a look at the bottom left on the image to see the received signal strength.

 

 

 

 

As well as the operating system tweaks for the audio output and recording levels there are some settings in WSJTX that need to be completed to tell the software which audio interfaces on the shack PC to use.

WSJT-X Settings screen (audio)
WSJT-X Settings screen (audio)
  • RIG – Radio interface settings – most common models of radio already have their comms settings built-in to WSJT-X, so simply select your radio.
  • CAT CONTROL – Connecting to the radio’s CAT/DATA port for controlling the radio. Typically the interface will appear as a serial COM port.
  • PTT – So that the PC can put the radio into transmit, the software needs to know how to trigger Transmit. Often this will be a separate COM port that needs setting up in the software
WSJT-X Settings screen (radio / PTT)
WSJT-X Settings screen (audio)

As well as the audio settings, Your computer’s clock does have to be very accurate with FT8. I use the Dimension 4 for keeping my clock accurate. This runs in the background and uses NTP to keep your clock in-sync to one of the online atomic clock servers periodically.

Anyway give it a shot, even if you are a foundation licence holder you can make some great contacts using 10w and a modest antenna!

Enjoy your radio !

2E0EFP