FT8 - Quick Intro

Introduction

A few people have asked me about the amateur radio thing, "why" being the most frequent. 

I will touch on this in more detail as time goes on but in short, when I was a kid, I'd wonder, when looking at a normal FM radio, why does it start at 88? Why does it end at 108? What is before and after these numbers.

Do you ever remember tuning into a radio when you were younger, hearing some random noises or foreign voices and wonder what it was you were picking up? Remember often hearing stuff from Eastern Europe during the cold war - who were those people hidden behind the Iron Curtain and what were they saying? How was I picking them up and from where?

I later found out that this is a great range for widely broadcast services due to the size of antenna needed to receive these signals clearly - and for a whole host of other reasons.

So, the short answer as to why - 

No, I'm not especially interested in chatting to sweaty truckers racing up the A1 with a delivery for Aldi (no offence to anyone harmed in the drafting of this sentence). 

That is an old-fashioned view and tends to refer more to CB, which is an unlicensed band that anyone can access. 

Modern radio amateurs do so because they are inquisitive and can combine their own comms knowledge with IT knowledge. The whole rationale for obtaining a licence is that it allows the person to learn and experiment.

Whilst it may not be for everyone, it fits in quite nicely with my knowledge and skillset.

There are a lot of ways you can make use of radio equipment these days to answer some of these questions. I'll probably do a few posts on each as time goes on. This post will make a start with FT8. It may be technical, boring for most but for those who asked the kinds of questions I did, may be of interest.

It is worth starting by saying - you do not need an amateur licence to receive FT8 but you do if you wish to transmit your own messages. 

I am only receiving at present mainly due to the fact I need some new gear to transmit on these bands. That is on my to-do list for the next few months!

So what is FT8?

In the simplest terms, it is a type of messaging format, perhaps best compared with text messages on a phone, but instead of privately sending them to an individual, or group, these are transmitted unencrypted around the world.

People use it to see how far they are able to send/receive radio comms. 

It is designed to work with a low SNR (in short - for poor quality signals) which means they can be sent/received much further than say a voice message would be.

How is it received?

My setup here is relatively simple and inexpensive. I am using an RTL SDR V3 Software Defined Radio (basically, a USB dongle which can tune into radio frequencies) an antenna (aerial) and a computer with a number of different software applications installed.

The process is relatively straightforward, in order to make use of FT8 signals you need to:

• Receive them (SDR Dongle/Antenna/SDR Console Application)
• Decode them (WSJTX Application)
• Present them in a "useful" format (Gridtracker).

Receive/SDR

I think it is fair to assume we all understand what it means to "tune in" a radio. In order to receive FT8 I use SDR Console. This is the first software element of the process - allowing you to tune in to the relevant frequency, in the example below 24.915mhz.

The image shows two main elements of receiving signals via an SDR. The frequency band at the top - is there a signal? The spikes indicate there is.

Below that, the waterfall shows how the signal has been received over time with the most recent at the top. This continuously updates so you can see breaks/gaps etc but that isn't particularly important here.

Receive in simple terms:

1. Plug in an SDR Dongle.
2. Install the drivers.
3. Connect the dongle to a suitable antenna (those which come with the dongle are perfectly adequate to get started).
4. Install an SDR application - SDR Console in this case.
5. Tune in to a relevant frequency, in this case 24.915mhz.
6. Set the receive mode to USB (upper sideband) and filter to 3khz.
7. Install and configure a Virtual Audio Cable, pipe the output to WSJTX.

Decode

WSJTX is the programme specifically designed for FT8 and is a quick and straightforward download/install. Providing you have completed all steps in the Receive part of the process, configuration requires only a quick check of the settings to ensure Input is set to the virtual audio cable.

Note: FT8 is time dependent so ensuring your computer time is always up to date is critical - if it isn't you won't receive anything. 

I use Nettime to ensure the time is continuously synched. Again, a basic app you can download, install and more or less forget about.

Assuming you have followed every step so far, when running the application, you will see messages start to come through.

Messages are sent/received every 15 seconds and both senders and recipients must have exactly the same time (hence the time synch).

The messages below include time, signal strength in dB (more on decibels another time I think), frequency and the actual content which in most cases will mean very little to most people.

This is where the next stage - presentation comes into play.

Presentation

Some people are happy enough with the content of the WSTJX messages - they can understand the meaning of each without a visual representation. Me, I prefer to see data presented in a more user friendly format so I use Gridtracker. This application imports the messages from WSJTX in real-time and plots the source/destination on a map.

The world is divided up into a grid and, where a message contains a grid-reference, it will fill in that square on a map as per below.

In the example below, even with the standard RTL dongle "kit" I'm able to receive messages from at least three continents. Having ran this a few times in the past, it never ceases to amaze me where people transmit from - quite often the middle of the ocean, Antarctica and elsewhere.

Alongside the mapping, Gridtracker provides a rolling update of incoming messages in a far more user friendly format than WSJTX

Conclusion

In the past, we would only really know where a signal was coming from if:

• The person broadcasting/transmitting told us directly.
• We knew where the radio station was located.
• We could make an assumption from the language being spoken.

FT8 allows amateur radio operators around the world to test propagation - how far their signals reach and where they are received.

Many feed their data back online in real time so senders can see a similar view of their own reach - or they configure WSJTX to send replies acknowledging the original message. I guess that's the next stage on this for me but for the time being, I find it quite interesting to be able to see this information and what factors affect it - for instance, time of day, solar cycle, atmospheric pressure and so on.